NCP1219BD65R2G - ON Semiconductor

October, 2009 − Rev. 3

1Publication Order Number:

NCP1219/D

NCP1219

PWM Controller with

Adjustable Skip Level and

External Latch Input

The NCP1219 represents a new, pin to pin compatible, generation

of the successful 7−pin current mode NCP12XX product series. The

controller allows for excellent standby power consumption by use of

its adjustable skip mode and integrated high voltage startup FET.

Internal frequency jittering, ramp compensation, timer−based fault

detection and a latch input make this controller an excellent

candidate for converters where ruggedness and component cost are

the key constraints.

The Dynamic Self Supply (DSS) drastically simplifies the

transformer design in avoiding the use of an auxiliary winding to

supply the NCP1219. This feature is particularly useful in

applications where the output voltage varies during operation (e.g.

battery chargers). Due to its high voltage technology, the IC can be

directly connected to the high voltage dc rail.

Features

•Fixed−Frequency Current−Mode Operation with Ramp

Compensation (65 kHz and 100 kHz Options)

•Dynamic Self Supply Eliminates the Need for an Auxiliary Winding

•Timer−Based Fault Protection for Improved Overload Detection

•Cycle Skip Reduces Input Power in Standby Mode

•Latch and Auto−Recovery Overload Protection Options

•Internal High Voltage Startup Circuit

•Accurate Current Limit Detector (±5%)

•Adjustable Skip Level

•Latch Input for Easy Implementation of Overvoltage and

Overtemperature Protection

•Frequency Modulation for Softened EMI Signature

•500 mA/800 mA Peak Source/Sink Current Drive Capability

•Pin to Pin Compatible with the Existing NCP12XX Series

•These Devices are Pb−Free and Halogen Free/BFR Free*

Typical Applications

•AC−DC Adapters for Notebooks, LCD Monitors

•Offline Battery Chargers

•Consumer Electronic Appliances STB, DVD, DVDR

*For additional information on our Pb−Free strategy and soldering details, please

download the ON Semiconductor Soldering and Mounting Techniques Reference

Manual, SOLDERRM/D.

SOIC−7

D SUFFIX

CASE 751U

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PIN CONNECTIONS

(Top View)

1219 = Specific Device Code

X = Overcurrent

= (A = latch, B = auto−retry)

Z = Frequency

= (6 = 65 kHz, 1 = 100 kHz)

A = Assembly Location

L = Wafer Lot

Y = Year

W = Work Week

G= Pb−Free Package

1219XZ

ALYW

MARKING DIAGRAM

VCC

Drv

GND

Skip/latch

See detailed ordering and shipping information in the package

dimensions section on page 19 of this data sheet.

ORDERING INFORMATION

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Figure 1. Typical Application Circuit

NCP1219

Voltage

Input

Output

EMI

Filter

−

* Optional

latch input*

Rramp*

DRV

VCC

Skip/latch

GND

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Figure 2. Functional Block Diagram

LEB

Skip/latch

7.5%* Jittering

Oscillator

DRV

GND

PWM

VFB(open)

VFB

latch−off, reset when

VCC(on)

Normal = VCC(min)

Fault = VCC(hiccup)

Istart when VCC > Vinhibit

Iinhibit when VCC < Vinhibit

VCS

VCC

Rskip

RCS

Rramp

16.7k*

UVLO

Latched overload

(Option A)

Vlatch

Skip

Comparator

2 V

50 ms*

filter

VSkip/latch

VSkip(max)

VSkip

51.3k*

Rupper

42.0k*

Rlower

VDD

Iramp(peak)

Iramp

TSD

75 ms*

filter

VCC < VCC(reset)

VCC(reset)

−

disable

internal

bias

Maximum

Duty Ratio

detect

VFB / 3

tOVLD

soft−

start

set

Fault

Management

Double Hiccup

Counter

clamp

detect

time

VILIM

tSSTART

Soft−Start/PWM Clamp

timer

reset

(Option A)

* Typical values are shown

SQR

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Table 1. PIN FUNCTION DESCRIPTION

Pin Name Description

1 Skip/latch This pin provides a latch input to permanently disable the device under a fault condition. It also allows the user to

adjust the skip threshold. A resistor between this pin and GND provides noise immunity to the latch input and sets

the skip threshold. The voltage on this pin is determined by the combination of the internal voltage divider and the

external resistor to ground. The default skip threshold is 1.1 V (typical) if no external resistor is used. An internal

clamp prevents the skip level from increasing above 1.3 V if the Skip/latch pin is pulled high to latch the controller.

2 FB The voltage on this pin is proportional to the output load on the converter. An internal resistor divider sets the

voltage on this pin above the regulation threshold (3 V) and an external optocoupler pulls the pin low to achieve

regulation. While the FB voltage is above its regulation threshold, the overload timer is enabled. If the overload

timer expires, the controller enters a double hiccup mode (option B) or is latched (option A) depending on the ver-

sion of the device. The converter enters skip mode if the FB voltage is below the skip threshold.

3 CS A voltage ramp proportional to the primary current is applied to this pin. The maximum current is reached once the

ramp voltage reaches 1 V (typical). A 100 mA (typical) current source provides ramp compensation. The amount of

ramp compensation is adjusted with a series resistor between the CS pin and the current sense resistor.

4 GND Analog ground.

5 DRV Main output of the PWM Controller. DRV has a source resistance of 12.6 W (typical) and a sink resistance of 6.7 W

(typical).

6 VCC Positive input supply. This pin connects to an external capacitor for energy storage. An internal current source

supplies current from the HV pin to this pin. Once the VCC voltage reaches VCC(on) (12.7 V typical), the current

source turns off and the DRV is enabled. The current source turns on once VCC falls to VCC(min) (9.9 V typical).

This mode of operation is known as dynamic self supply (DSS).

If the bias current consumption exceeds the startup current, and VCC drops 0.5 V (typical) below VCC(min) the con-

verter turns off and enters a double hiccup mode. If the VCC voltage is below 0.67 V (typical) the startup current is

reduced to 200 mA (typical), reducing power dissipation.

8 HV This is the input of the high voltage startup regulator and connects directly to the bulk voltage. A controlled current

source supplies current from this pin to the VCC capacitor, eliminating the need for an external startup resistor. The

charge current is 12.8 mA (typical).

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Table 2. MAXIMUM RATINGS (Notes 1 − 4)

Rating Symbol Value Unit

HV Voltage VHV −0.3 to 500 V

HV Current IHV 100 mA

Supply Voltage VCC −0.3 to 20 V

Supply Current ICC 100 mA

Skip/latch Voltage VSkip/latch −0.3 to 9.5 V

Skip/latch Current ISkip/latch 100 mA

FB Voltage VFB −0.3 to 5.0 V

FB Current IFB 100 mA

CS Voltage VCS −0.3 to 5.0 V

CS Current ICS 100 mA

DRV Voltage VDRV −0.3 to 20 V

DRV Current IDRV −500 to 800 mA

Operating Junction Temperature TJ–40 to 150 °C

Storage Temperature Range Tstg –60 to 150 °C

Power Dissipation (TA = 25°C, 2.0 Oz Cu, 1.0 Sq Inch Printed Circuit Copper Clad)

D Suffix, Plastic Package Case 751U (SOIC−7) (Note 4)

PD0.92

Thermal Resistance, Junction to Ambient (2.0 Oz Cu Printed Circuit Copper Clad)

D Suffix, Plastic Package Case 751U (SOIC−7)

Junction to Air, Low conductivity PCB (Note 3)

Junction to Lead, Low conductivity PCB (Note 3)

Junction to Air, High conductivity PCB (Note 4)

Junction to Lead, High conductivity PCB (Note 4)

RθJA

RθJL

RθJA

RθJL

177

136

°C/W

Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the

Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect

device reliability.

1. This device series contains ESD protection and exceeds the following tests:

Pins 1– 6: Human Body Model 3000 V per JEDEC JESD22−A114−F.

Pins 1– 6: Machine Model Method 300 V per JEDEC JESD22−A115−A.

Pin 8 is the HV startup of the device and is rated to the maximum rating of the part, or 500 V.

2. This device contains Latch−Up protection and exceeds ±100 mA per JEDEC Standard JESD78.

3. As mounted on a 40x40x1.5 mm FR4 substrate with a single layer of 80 mm2 of 2 oz copper traces and heat spreading area. As specified for

a JEDEC 51 low conductivity test PCB. Test conditions were under natural convection or zero air flow.

4. As mounted on a 40x40x1.5 mm FR4 substrate with a single layer of 650 mm2 of 2 oz copper traces and heat spreading area. As specified

for a JEDEC 51 high conductivity test PCB. Test conditions were under natural convection or zero air flow.

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Table 3. ELECTRICAL CHARACTERISTICS (VHV = 60 V, VCC = 11.3 V, VFB = 2 V, VSkip/latch = 0 V, VCS = 0 V, VDRV = open, CCC =

0.1 mF, for typical values TJ = 25°C, for min/max values, TJ is –40°C to 125°C, unless otherwise noted)

Characteristics Conditions Symbol Min Typ Max Unit

STARTUP AND SUPPLY CIRCUITS

Supply Voltage

Startup Threshold

Minimum Operating Voltage

Undervoltage Lockout

Double Hiccup Threshold

Logic Reset Voltage

VCC Increasing

VCC Decreasing

VCC(on)

VCC(MIN)

UVLO

VCC(hiccup)

VCC(reset)

11.2

9.0

8.4

4.9

–

12.7

9.9

9.4

5.7

4.0

13.8

10.8

10.6

6.3

–

UVLO Filter Delay tUVLO(delay) – 50 – ms

Inhibit Threshold Voltage Iinhibit = 500 mA Vinhibit 0.35 0.67 0.90 V

Inhibit Bias Current VCC = 0 V Iinhibit 100 200 350 mA

Minimum Startup Voltage Istart = 0.5 mA, VCC = VCC(on) – 0.5 V Vstart(min) – 20 28 V

Startup Current VCC = VCC (on) – 0.5 V Istart 5.5 12.8 18.5 mA

Startup Circuit Reverse Current VHV = 0 V, VCC = 14 V IHV(reverse) – – 100 mA

Off−State Leakage Current VHV = 500 V, VCC = 14 V IHV(off) – 12 50 mA

Breakdown Voltage (Note 5) IHV = 50 mA VBR(DS) 500 – – V

Supply Current

Device Disabled/Fault

Device Enabled/No Switching

Device Switching (65 kHz)

Device Switching (100 kHz)

VSkip/latch = 5.2 V, VFB = open

VSkip/latch = open, VFB = 0 V

VSkip/latch = open, CDRV = 1000 pF

ICC1

ICC2

ICC3A

ICC3B

–

0.6

1.4

2.2

2.4

0.8

2.1

2.7

3.2

CURRENT SENSE

Current Sense Voltage Threshold Apply voltage step on CS pin VILIM 0.95 1.0 1.05 V

Leading Edge Blanking Duration tLEB 100 184 330 ns

Propagation Delay VCS > VILIM to 50% DRV turns off,

CDRV = 1000 pF

tdelay – 59 150 ns

Ramp Compensation Peak Current Iramp(peak) – 100 – mA

Ramp Compensation Valley Current Iramp(valley) – 0 – mA

FEEDBACK INPUT

Open Feedback Voltage VFB(open) 3.2 3.6 3.9 V

Internal Pull−up Resistance RFB – 16.7 – kW

Feedback Pull−up Current VFB = 0 V IFB 141 280 392 mA

Feedback to Current Set Point Ratio Iratio – 3.0 –

SOFT−START

Soft−Start Period Measured at 0.9 VILIM tSSTART – 4.8 – ms

OSCILLATOR

Oscillator Frequency

65 kHz Option

100 kHz Option

TJ = 25_C

TJ = −40_C to 85_C

TJ = −40_C to 125_C

TJ = 25_C

TJ = −40_C to 85_C

TJ = −40_C to 125_C

fOSC

61.75

–

100

–

68.25

105

107

kHz

Frequency Modulation in

Percentage of fOSC

–±7.5 – %

Frequency Modulation Period – 6.0 – ms

Maximum Duty Ratio D 75 80 85 %

5. Guaranteed by the IHV(off) test.

6. Guaranteed by design only.

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Table 3. ELECTRICAL CHARACTERISTICS (VHV = 60 V, VCC = 11.3 V, VFB = 2 V, VSkip/latch = 0 V, VCS = 0 V, VDRV = open, CCC =

0.1 mF, for typical values TJ = 25°C, for min/max values, TJ is –40°C to 125°C, unless otherwise noted)

Characteristics UnitMaxTypMinSymbolConditions

GATE DRIVE

Drive Resistance

DRV Sink

DRV Source

VFB = 0 V, VDRV = 1 V

VDRV = VCC – 1 V

RSNK

RSRC

2.0

6.0

6.7

12.6

Rise Time (10% to 90%) CDRV = 1000 pF (10% to 90%) tr– 30 – ns

Fall Time (90% to 10%) CDRV = 1000 pF (90% to 10%) tf– 20 – ns

LATCH INPUT

Latch Voltage Threshold Vlatch 3.4 3.9 4.6 V

Latch Filter Delay VSkip/latch = 5.2 V, apply voltage step

on Skip/latch pin

tlatch(delay) – 50 – ms

CYCLE SKIP

Default Skip Threshold VFB increasing, VSkip/latch = Open Vskip 0.9 1.1 1.3 V

Skip Clamp Voltage VFB increasing, VSkip/latch = 2.0 V Vskip(MAX) 1.1 1.3 1.5 V

Skip Comparator Hysteresis VFB decreasing, VSkip/latch = 0.5 V Vskip(HYS1) – 75 – mV

Skip Clamp Comparator

Hysteresis

VFB decreasing, VSkip/latch = 2.0 V Vskip(HYS2) – 75 – mV

Skip Current VSkip/latch = 0 V Iskip 30 47 56 mA

FAULTS PROTECTION

Thermal Shutdown (Note 6) Temperature Increasing TSHDN – 155 – °C

Thermal Shutdown Hysteresis Temperature Decreasing TSHDN(HYS) – 40 – °C

Thermal Shutdown Delay TSHDN(delay) – 75 – ms

Overload Timer Apply voltage step on FB pin tOVLD –118 – ms

5. Guaranteed by the IHV(off) test.

6. Guaranteed by design only.

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TYPICAL CHARACTERISTICS

Figure 3. Supply Voltage Thresholds vs.

Junction Temperature

Figure 4. Inhibit Threshold Voltage vs.

Junction Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

0.14

0.42

0.56

0.70

0.98

1.26

1.40

Figure 5. Inhibit Current vs. Junction

Temperature

Figure 6. Startup Current vs. Junction

Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

100

120

140

180

220

240

280

300

1251007550250−25−50

10.0

10.5

11.5

12.0

12.5

13.5

14.0

15.0

Figure 7. Startup Current vs. Supply Voltage Figure 8. Startup Circuit Leakage Current vs.

Junction Temperature

VCC, SUPPLY VOLTAGE (V) TJ, JUNCTION TEMPERATURE (°C)

18161086420

1251007550250−25−50

VCC, SUPPLY VOLTAGE

THRESHOLDS (V)

Vinhibit, INHIBIT THRESHOLD

VOLTAGE (V)

Iinhibit, INHIBIT CURRENT (mA)

Istart, STARTUP CURRENT (mA)

Istart(off), STARTUP CIRCUIT

LEAKAGE CURRENT (mA)

150

0.28

0.84

1.12

Iinhibit = 500 mA

VCC(on)

VCC(MIN)

UVLO

VCC(reset)

150

160

200

260

VCC = 0 V VHV = 60 V

VCC = VCC(on) − 0.5 V

150

11.0

13.0

14.5

12 14 20

VHV = 60 V

150

VHV = 60 V

VCC = 14 V

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TYPICAL CHARACTERISTICS

Figure 9. Startup Circuit Leakage Current vs.

HV Voltage

Figure 10. Supply Current vs. Junction

Temperature

VHV, HV VOLTAGE (V) TJ, JUNCTION TEMPERATURE (°C)

450375300 525225150750

Figure 11. Operating Supply Current vs.

Supply Voltage

Figure 12. Current Sense Voltage Threshold

vs. Junction Temperature

VCC, SUPPLY VOLTAGE (V) TJ, JUNCTION TEMPERATURE (°C)

2119171513119

0.5

1.0

1.5

2.0

3.0

3.5

4.0

1251007550250−25−50

0.95

0.96

0.98

1.00

1.02

1.04

1.05

Figure 13. Leading Edge Blanking Time vs.

Junction Temperature

Figure 14. Current Sense Propagation Delay

vs. Junction Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

100

120

140

160

180

200

220

240

1251007550250−25−50

105

Istart(off), STARTUP CIRCUIT

LEAKAGE CURRENT (mA)

ICC, SUPPLY CURRENT (mA)

ICC3, OPERATING SUPPLY CURRENT (mA)

VILIM, CURRENT SENSE VOLTAGE

THRESHOLD (V)

tLEB, LEADING EDGE BLANKING TIME (ns)

tdelay, CURRENT SENSE

PROPAGATION DELAY (ns)

TJ = −40°C

TJ = 125°C

2.5

TJ = 25°C

150

150 150

ICC3 (fOSC ~ 65 kHz)

ICC2

ICC1

201816141210

0.97

0.99

1.01

1.03

260

280

300

115

125

VCC = 14 V

fOSC = 65 kHz

0.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

2.7

3.0

−50 −25 0 25 50 75 100 125 150

ICC3 (fOSC ~ 100 kHz)

fOSC = 100 kHz

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TYPICAL CHARACTERISTICS

Figure 15. Oscillator Frequency vs. Junction

Temperature

Figure 16. Maximum Duty Ratio vs. Junction

Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

Figure 17. Drive Sink and Source Resistances

vs. Junction Temperature

Figure 18. Latch Voltage Threshold vs.

Junction Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

3.0

3.2

3.4

3.8

4.2

4.4

4.6

5.0

Figure 19. Default Skip Threshold vs. Junction

Temperature

Figure 20. Skip Clamp Voltage vs. Junction

Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

0.80

0.85

0.90

1.00

1.05

1.10

1.25

1.30

1251007550250−25−50

1.05

1.10

1.15

1.25

1.30

1.40

1.50

1.55

fOSC, OSCILLATOR FREQUENCY (kHz)

D, MAXIMUM DUTY RATIO (%)

RSNK/RSRC, DRIVE SINK/SOURCE

RESISTANCE (W)

Vlatch, LATCH VOLTAGE THRESHOLD (V)

Vskip, DEFAULT SKIP THRESHOLD (V)

Vskip(MAX), SKIP CLAMP VOLTAGE (V)

150

Source, VDRV = VCC − 1 V

Sink, VDRV = 1 V

150

3.6

4.0

4.8

0.95

1.15

1.20

150

VSkip/latch = open VSkip/latch = 2 V

150

1.20

1.35

1.45

VCC = 11.3 V

100

110

120

−50 −25 0 25 50 75 100 125 150

65 kHz Option

100 kHz Option

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TYPICAL CHARACTERISTICS

Figure 21. Adjustable Skip Threshold vs.

Junction Temperature

Figure 22. Skip Threshold vs. Skip Resistor

TJ, JUNCTION TEMPERATURE (°C) RSkip, EXTERNAL SKIP RESISTOR (kW)

1251007550250−25−50

0.2

0.3

0.4

0.5

0.7

0.8

0.9

1.0

1000100101

0.2

0.4

0.6

0.8

1.0

1.2

Figure 23. Soft−Start Period vs. Junction

Temperature

Figure 24. Overload Timer Period vs. Junction

Temperature

TJ, JUNCTION TEMPERATURE (°C) TJ, JUNCTION TEMPERATURE (°C)

1251007550250−25−50

105

110

120

125

135

140

Vskip2, ADJUSTABLE SKIP THRESHOLD (V)

Vskip, SKIP THRESHOLD (V)

tSSTART

, SOFT−START PERIOD (ms)

tOVLD, OVERLOAD TIMER PERIOD (ms)

150

0.6

Rskip = 48.7 kW

10000

150

100

115

130

1.1

1.2

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DETAILED OPERATING DESCRIPTION

The NCP1219 is part of a product family of current mode

controllers designed for ac−dc applications requiring low

standby power. The controller operates in skip or burst

mode at light load. Its high integration reduces component

count resulting in a more compact and lower cost power

supply. This device family has 2 options, A and B. Option

A latches where as option B auto restarts after an overload

fault.

The internal high voltage startup circuit with dynamic

self supply (DSS) allows the controller to operate without

an auxiliary supply, simplifying the transformer design.

This feature is particularly useful in applications where the

output voltage varies during operation (e.g. printer

adapters).

Other features found in the NCP1219 are frequency

jittering, adjustable ramp compensation, timer based fault

detection and a dedicated latch input.

High Voltage Startup Circuit

The NCP1219 internal high voltage startup circuit

eliminates the need for external startup components and

provides a faster startup time compared to an external

startup resistor. The startup circuit consists of a constant

current source that supplies current from the HV pin to the

supply capacitor on the VCC pin (CCC). The HV pin is rated

at 500 V allowing direct connection to the bulk capacitor.

The start−up current (Istart) is typically 12.8 mA.

The startup current source is disabled once the VCC

voltage reaches VCC(on), typically 12.7 V. The controller is

then biased by the VCC capacitor. The current source is

enabled once the VCC voltage decays to its minimum

operating threshold (VCC(MIN)) typically 9.9 V. If the

supply current consumption exceeds the startup current,

VCC will decay below VCC(MIN). The NCP1219 has an

undervoltage lockout (UVLO) to prevent operation at low

VCC levels. The UVLO threshold is typically 9.4 V. The

DRV signal is immediately disabled upon reaching UVLO.

It is re−enabled if VCC increases above UVLO before the

50 ms (typical) timer expires. Otherwise, the controller

enters double hiccup mode.

The controller enters a double hiccup mode if an

overload (option B), thermal shutdown, UVLO or latch

fault is detected. A double hiccup fault disables the DRV

signal, sets the controller in a low current mode and allows

VCC to discharge to VCC(hiccup), typically 5.7 V. This cycle

is repeated twice to minimize power dissipation in external

components during a fault event. Figures 25 and 26 show

double hiccup mode operation with a fault occurring while

the startup circuit is disabled and enabled, respectively. A

soft−start sequence is initiated the second time VCC reaches

VCC(on). If the fault is present or the controller is latched

upon reaching VCC(on), the controller stays in hiccup mode.

During this mode, VCC never drops below 4 V, the

controller logic reset level. This prevents latched faults

from being cleared unless power to the controller is

completely removed (i.e. unplugging the supply from the

AC line). There are two options available in the NCP1219,

options A and B. Option A latches off after the overload

timer expires if an overload fault is detected. In this case,

VCC cycles between VCC(on) and VCC(hiccup) without

enabling the DRV signal until the power to the controller

is reset. On the other hand, option B has auto−retry circuitry

allowing the DRV signal to restart after a double hiccup

sequence triggered by an overload condition.

UVLO

Fault1

DRV ON OFF ON

Fault

Figure 25. VCC Double Hiccup Operation with a Fault Occurring While the Startup Circuit is Disabled.

VCC(reset)

VCC(on)

VCC(MIN)

VCC(hiccup)

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ON OFF ON

Fault

Figure 26. VCC Double Hiccup Operation with a Fault Occurring While the Startup Circuit is Enabled

UVLO

Fault2

DRV

VCC(reset)

VCC(on)

VCC(MIN)

VCC(hiccup)

An internal supervisory circuit monitors the VCC voltage

to prevent the controller from dissipating excessive power

if the VCC pin is accidentally grounded. A lower level

current source (Iinhibit) charges CCC from 0 V to Vinhibit,

typically 0.67 V. Once VCC exceeds Vinhibit, the startup

current source is enabled. This behavior is illustrated in

Figure 27. This slightly increases the total time to charge

VCC, but it is generally not noticeable.

Figure 27. Startup Current at Various VCC Levels

VCC

VCC(on)

VCC(MIN)

Vinhibit

Startup Current

Istart

Iinhibit

The start−up circuit is rated at a maximum voltage of

500 V. If the device operates in the DSS mode, power

dissipation should be controlled to avoid exceeding the

maximum power dissipation of the controller. If dissipation

on the controller is excessive, a resistor can be placed in

series with the HV pin. This will reduce power dissipation

on the controller and transfer it to the series resistor.

Standby mode losses and normal mode power dissipation

can be reduced by biasing the controller with an auxiliary

winding. The auxiliary winding needs to maintain VCC

above VCC(MIN) once the startup circuit is disabled.

The power dissipation of the controller when operated in

DSS mode, PDSS, can be calculated using equation 1, where

ICC3 is the operating current of the NCP1219 during

switching and VHV is the voltage at the HV pin. The HV pin

is most often connected to the bulk capacitor.

PDSS +ICC3 @(VHV *VCC)(eq. 1)

In comparison, the power dissipation when the startup

circuit is disabled and VCC is being supplied by the

auxiliary winding is a function of the VCC voltage. This is

shown in Equation 2.

PAUX +ICC3 @VCC (eq. 2)

It is recommended that an external filter capacitor be

placed as close as possible to the VCC pin to improve the

noise immunity.

Soft−Start Operation

Figures 28 and 29 show how the soft−start feature is

included in the pulse−width modulation (PWM)

comparator. When the NCP1219 starts up, a soft−start

voltage VSSTART begins at 0 V. VSSTART increases

gradually from 0 V to 1.0 V in 4.8 ms and stays at 1.0 V

afterward. VSSTART is compared with the divided by 3

feedback pin voltage (VFB/3). The lesser of VSSTART and

(VFB/3) becomes the modulation voltage, VPWM, in the

PWM duty ratio generation. Initially, (VFB/3) is above

1.0 V because the FB pin is brought to VFB(open), typically

3.6 V, by the internal pullup resistor. As a result, VPWM is

limited by the soft−start function and slowly ramps up the

duty ratio (and therefore the primary current) for the initial

4.8 ms. This provides a greatly reduced stress on the power

devices during startup.

Figure 28. VPWM is the lesser of VSSTART and (VFB/3)

−

)

VPWM

VSSTART

VFB/3

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Figure 29. Soft−Start (Time = 0 at VCC = VCC(on))

time

time must be less than tOVLD

to prevent fault condition

time

1 V

Soft−start voltage, VSSTART

tSSTART

1 V

Feedback pin voltage divided by 3, VFB/3

tSSTART

Drain Current, ID

1 V

Pulse Width Modulation voltage, VPWM

Current−Mode Pulse Width Modulation

The NCP1219 is a current−mode, fixed frequency pulse

width modulation controller with ramp compensation. The

PWM block of the NCP1219 is shown in Figure 30. The

DRV signal is enabled by a clock pulse. At this time,

current begins to flow in the power MOSFET and the sense

resistor. A corresponding voltage is generated on the CS

pin of the device, ranging from very low to as high as the

maximum modulation voltage, VPWM (maximum of 1 V).

This sets the primary current on a cycle−by−cycle basis.

Equation 3 gives the maximum drain current, ID(MAX),

where RCS is the current sense resistor value and VILIM is

the current sense voltage threshold.

ID(MAX) +VILIM

RCS

(eq. 3)

Figure 30. Current−Mode Implementation

LEB

PWM

Output

180 ns

−

(1 V max. signal)

Clock

Iramp(peak)

Vbulk

RCS

VCS

80%

max duty

VPWM

Iramp

Figure 31 shows the timing diagram for the

current−mode pulse width modulation operation. An

internal clock sets the output RS latch, pulling the DRV pin

high. The latch is then reset when the voltage on the CS pin

intersects the modulation voltage, VPWM. This generates

the duty ratio of the DRV pulse. The maximum duty ratio

is internally limited to 80% (typical) by the output RS latch.

Figure 31. Current−Mode Timing Diagram

PWM

Output

clock

VPWM

VCS

The VPWM voltage is the scaled representation of the FB

pin voltage. The scale factor, Iratio, is 3. The FB pin voltage

is provided by an external error amplifier, whose output is

a function of the power supply output. An FB signal

between Vskip and 3 V determines the duty ratio of the

controller output. The FB voltage operates in a closed loop

with the output voltage to regulate the power supply.

It is recommended that an external filter capacitor be

placed as close to the FB pin as possible to improve the

noise immunity.

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Ramp Compensation

Ramp compensation is a known mean to cure

subharmonic oscillations. These oscillations take place at

half the switching frequency and occur only during

continuous conduction mode (CCM) with a duty ratio

greater than 50%. To lower the current loop gain, one

usually injects 50 to 75% of the inductor current down

slope. The NCP1219 generates an internal current ramp

that is synchronized with the clock. This current ramp is

then routed to the CS pin. Figures 32 and 33 depict how the

ramp is generated and utilized. Ramp compensation is

simply formed by placing a resistor, Rramp, between the CS

pin and the sense resistor.

Figure 32. Internal Ramp Compensation Current

Source

0time

80% of period

100% of period

Iramp(peak)

Ramp current, Iramp

Figure 33. Inserting a Resistor in Series with the

Current Sense Information Provides Ramp

Compensation

Clock

Oscillator

DRV

Current

Ramp

Iramp(peak)

Rramp

RCS

In order to calculate the value of the ramp compensation

resistor, Rramp, the off time primary current slope,

Soff,primary must be calculated using Equation 4,

Soff,primary +

(Vout )Vf)@ǒNP

NSǓ

(eq. 4)

where V

out is the converter output voltage, Vf is the forward

diode drop of the secondary diode, NP/NS is the primary to

secondary turns ratio, and LP is the primary inductance of

the transformer. The value of Rramp can be calculated using

Equation 5,

Rramp +ǒSoff,primary RCSǓ@%slope

ǒIramp(peak) fOSC

DǓ(eq. 5)

where RCS is the current sense resistor and %slope is the

percentage of the current downslope to be used for ramp

compensation.

The NCP1219 has a peak ramp compensation current of

100 mA. A frequency of 65 kHz with an 80% maximum

duty ratio corresponds to an 8.1 mA/ms ramp. For a typical

flyback design, let’s assume that the primary inductance is

350 mH, the converter output is 19 V, the Vf of the output

diode is 1 V and the NP:NS ratio is 10:1. The off time

primary current slope is given by Equation 6.

(Vout )Vf)ǒNP

NSǓ

LP+571 mA

ms(eq. 6)

When projected over an RCS of 0.1 W (for example), this

becomes 57 mV/ms. If we select 50% of the downslope as

the required amount of ramp compensation, then we shall

inject 28.5 mV/ms. Therefore, Rramp is simply equal to

Equation 7.

Rramp +28.5 mV

8.1 mA

+3.5 kW(eq. 7)

Ramp compensation greater than 50% of the inductor

down slope can be used if necessary; however,

overcompensating will degrade the transient response of

the system. The addition of ramp compensation also

reduces the total available output power of the system.

Internal Oscillator

The internal oscillator of the NCP1219 provides the

clock signal that sets the DRV signal high and limits the

duty ratio to 80% (typical). The oscillator has a fixed

frequency of 65 kHz or 100 kHz. The NCP1219 employs

frequency jittering to smooth the EMI signature of the

system by spreading the energy of the main switching

component across a range of frequencies. An internal low

frequency oscillator continuously varies the switching

frequency of the controller by ±7.5%. The period of

modulation is 6 ms, typical. Figure 34 illustrates the

oscillator frequency modulation.

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Figure 34. Oscillator Frequency Modulation

time

Oscillator Frequency

FOSC

− 7.5%

FOSC

+ 7.5%

FOSC

6 ms

Gate Drive

The output drive of the NCP1219 is designed to directly

drive the gate of an n−channel power MOSFET. The DRV

pin is capable of sourcing 500 mA and sinking 800 mA of

drive current. It has typical rise and fall times of 30 ns and

20 ns, respectively, driving a 1 nF capacitive load.

The power dissipation of the output stage while driving

the capacitance of the power MOSFET must be considered

when calculating the NCP1219 power dissipation. The

driver power dissipation can be calculated using

Equation 8,

PDRV +fOSC @QG@VCC (eq. 8)

where QG is the gate charge of the power MOSFET.

External Latch Input

Board level protection functionality is often

incorporated using external circuits to suit a specific

application. An external fault condition can be used to

disable the controller by bringing the voltage on the

Skip/latch pin above the latch threshold, Vlatch (3.9 V

typical). When an external fault condition is detected, the

DRV signal is stopped, and the controller enters low current

operation mode. The external capacitor CCC discharges

and VCC drops until VCC(hiccup) is reached. The high

voltage startup circuit turns on and Istart charges CCC until

VCC(on) is reached. VCC cycles between VCC(on) and

VCC(hiccup) until VCC reaches VCC(reset). Voltage must be

removed from the HV pin, disabling the startup current and

allowing CCC to discharge to VCC(reset). Therefore, the

controller is reset by unplugging the power supply from the

wall to allow Vbulk to discharge. Figure 35 illustrates the

timing diagram of VCC in the latch−off condition.

Figure 35. Latch−off VCC Timing Diagram

VCC(hiccup)

VCC(on)

Startup current source is

charging the VCC

capacitor

Startup current source is

off when V CC

is VCC(on)

Startup current source turns

on when VCC

reaches VCC(hiccup)

time

The external latch feature allows the circuit designers to

implement different kinds of latching protection. Figure 36

shows an example circuit in which a bipolar transistor is

used to pull the Skip/latch pin above the latch threshold.

The RLIM value is chosen to prevent the Skip/latch pin from

exceeding the maximum rated voltage. The NCP1219

applications note (AND8393/D) details several simple

circuits to implement overtemperature protection (OTP)

and overvoltage protection (OVP).

Figure 36. Circuit Example of an External

Latch−off Circuit

Rskip

Cskip

RLIM

VCC

NCP1219

Skip/latch

GND

CS VCC

DRV

Fault

output

An internal blanking filter prevents fast voltage spikes

caused by noise from latching the part. However, it is

recommended that an external filter capacitor be placed as

close as possible to the Skip/latch pin to further improve the

noise immunity.

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Skip Cycle Operation

During standby or light load operation the duty ratio on

the controller becomes very small. At this point, a

significant portion of the power dissipation is related to the

power MOSFET switching on and off. To reduce this power

dissipation, the NCP1219 “skips” pulses when the FB level

drops below the skip threshold. The level at which this

occurs is completely adjustable by setting a resistor on the

Skip/latch pin.

By discontinuing pulses, the output voltage slowly drops

and the FB voltage rises. When the FB voltage rises above

the Vskip level, DRV is turned back on. This feature

produces the timing diagram shown in Figure 37.

Figure 37. Skip Operation

skip

Skip

Skip peak current, %ICSSKIP

, is the percentage of the

maximum peak current at which the controller enters skip

mode. %ICSSKIP can be any value from 0 to 43% as defined

by Equation 9. However, the higher %ICSSKIP is, the greater

the drain current when skip is entered. This increases

acoustic noise. Conversely, the lower %ICSSKIP is, the

larger the percentage of energy is expended turning the

switch on and off. Therefore, it is important to adjust

%ICSSKIP to the optimal level for a given application.

%ICSSKIP +

Vskip

3V @100 (eq. 9)

Figure 38 shows the details of the Skip/latch pin

circuitry. The voltage on the Skip/latch pin determines the

voltage required on the FB pin to place the controller into

skip mode. If the pin is left open, the default skip threshold

is 1.1 V. This corresponds to a 37% %ICSSKIP (%ICSSKIP =

1.1 V / 3.0 V * 100% = 37%). Therefore, the controller will

enter skip mode when the peak current is less than 37% of

the maximum peak current.

Figure 38. Skip Adjust Circuit

Skip/latch S

R Q

VFB

latch-off, reset

when VCC < VCC(reset)

Rskip

Vlatch

Skip

Comparator

2 V

50 us

filter

Vskip/Latch

Vskip(MAX)

VSkip

51.3 k

Rupper

42.0 k

Rlower

Cskip

VSkip/latch

To DRV

latch

reset

The skip level is reduced by placing an external resistor,

Rskip, between the Skip/latch and GND pins. Figure 39

summarizes the operating voltage regions of the Skip/latch

pin.

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Figure 39. NCP1219 VSkip/latch Pin Operating

Regions

Controller is latched

Adjustable Vskip

range.

0 V (no skip)

Vskip(MAX)

(maximum skip threshold)

latch

9.5 V (maximum pin voltage)

skip/latch

Skip threshold clamped to Vskip(MAX)

Within the adjustable Vskip range, the skip level changes

according to Equation 10.

Vskip +2V@(Rlower øRskip)

(Rlower øRskip))Rupper

(eq. 10)

An internal clamp limits the skip threshold (Vskip(MAX))

to 1.3 V. Increasing the voltage on the Skip/latch pin

beyond the value of the internal clamp will induce no

further change in the skip level. This prevents the act of

disabling the controller in the presence of an external latch

event from causing it to enter skip mode. The relationship

between %ICSSKIP

, VSkip/latch, Vskip, and Rskip is

summarized in Table 4.

Table 4. %ICSskip and Skip Threshold Relationship with Rskip

%ICSskip VSkip/latch Vskip Rskip Comment

0% 0 V 0 V 0 WNever skips

12% 0.36 V 0.36 V 11.8 kW–

25% 0.75 V 0.75 V 52.3 kW–

37% 1.10 V 1.10 V Open Default Skip Threshold

43% 2.00 V 1.30 V –No further increase in Skip threshold

43 % 3.00 V 1.30 V –No further increase in Skip threshold

External Non−Latched Shutdown

Figure 40 summarizes the operating regions of the FB

pin. An external non−latched shutdown can be easily

implemented by simply pulling FB below the skip level.

This is an inherent feature of the standby skip operation,

allowing additional flexibility in the SMPS design.

Figure 40. NCP1219 Operation Threshold

Fault operation when staying

in this region longer than 118 ms

PWM operation

No DRV pulses

3 V

VFB

0 V

Vskip

Figure 41 shows an example implementation of a

non−latched shutdown circuit using a bipolar transistor to

pull the FB pin low.

Figure 41. Example Circuit for Non−Latched

Shutdown

NCP1219

OFF

opto

coupler

Skip/latch

GND

VCC

DRV

Overload Protection

Figure 42 details the timer based fault detection circuitry.

When an overload (or short circuit) event occurs, the output

voltage collapses and the optocoupler does not conduct

current. This opens the FB pin and VFB is internally pulled

higher than 3.0 V. Since VFB/3 is greater than 1 V, the

controller activates an error flag and starts a timer, tOVLD

(118 ms typical). If the output recovers during this time, the

timer is reset and the device continues to operate normally.

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However, if the fault lasts for more than 118 ms, then the

driver turns off and the device enters the VCC double hiccup

mode described earlier.

Figure 42. Block Diagram of Timer−Based Fault

Detection

Soft−start

118 ms

delay

1 V max

Fault

−

VSS

VFB

disable Drv

VFB

4.8 V

The NCP1219 also has an internal temperature shutdown

circuit. If the junction temperature of the controller reaches

155°C (typical), the driver turns off and the controller

enters double hiccup mode.

Latched and Auto−Retry Options

The NCP1219A offers a latched fault circuitry. An

overload fault condition detected by the controller results

in a latch−off shutdown, requiring the controller to be reset

by cycling VCC (removing the ac line input). NCP1219B

provides an auto−retry circuit. All fault conditions except

the external latch fault result in the controller entering

double hiccup mode, attempting to restart the controller

every other VCC cycle, as mentioned earlier.

Table 5. ORDERING INFORMATION

Device Overcurrent Frequency Package Shipping†

NCP1219AD65R2G Latch 65 kHz

SOIC−7 (Pb−Free) 2500 / Tape & Reel

NCP1219BD65R2G Auto−Recovery 65 kHz

NCP1219AD100R2G Latch 100 kHz

NCP1219BD100R2G Auto−Recovery 100 kHz

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

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PACKAGE DIMENSIONS

SOIC−7

CASE 751U−01

ISSUE D

SEATING

PLANE

X 45_

NOTES:

1. DIMENSIONING AND TOLERANCING PER

ANSI Y14.5M, 1982.

2. CONTROLLING DIMENSION: MILLIMETER.

3. DIMENSION A AND B ARE DATUMS AND T

IS A DATUM SURFACE.

4. DIMENSION A AND B DO NOT INCLUDE

MOLD PROTRUSION.

5. MAXIMUM MOLD PROTRUSION 0.15 (0.006)

PER SIDE.

DIM

MIN MAX MIN MAX

INCHES

4.80 5.00 0.189 0.197

MILLIMETERS

B3.80 4.00 0.150 0.157

C1.35 1.75 0.053 0.069

D0.33 0.51 0.013 0.020

G1.27 BSC 0.050 BSC

H0.10 0.25 0.004 0.010

J0.19 0.25 0.007 0.010

K0.40 1.27 0.016 0.050

M0 8 0 8

N0.25 0.50 0.010 0.020

S5.80 6.20 0.228 0.244

−A−

−B−

0.25 (0.010)

−T−

0.25 (0.010) TSAS

7 PL

____

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NCP1219/D

The products described herein (NCP1219) may be covered by one or more of the following U.S. patents: 6,271,735, 6,362,067, 6,385,060,

6,597,221, 6,633,193, 6,587,351, 6,940,320. There may be other patents pending.

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