LTC1798CS8-4.1#PBF - ANALOG DEVICES

LTC1798 Series

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TYPICAL APPLICATION

DESCRIPTION

Micropower Low

Dropout References

The LTC

1798/LTC1798-2.5/LTC1798-3/LTC1798-4.1/

LTC1798-5 are micropower bandgap references that

combine high accuracy and low drift with very low supply

current and small package size. The combination of ultralow

quiescent current and low dropout voltage of only 200mV

(max) makes them ideal for battery-powered equipment.

The output voltage is set by an external resistor divider

for the adjustable LTC1798.

This series of references uses curvature compensation to

obtain low temperature coefﬁcient and trimmed thin-ﬁlm

resistors to achieve high output accuracy. These references

can source up to 10mA and sink up to 2mA, making them

ideal for precision regulator applications. They are stable

without an output bypass capacitor, but are also stable

with capacitance up to 1µF. This feature is important in

critical applications where PC board space is a premium

and fast settling is demanded.

The LTC1798 series references provided power dissipation

advantages over shunt references. In addition to supply

current, shunt references must also idle the entire load

current to operate.

The LTC1798 series is available in the SO-8 package.

2.5V Battery-Powered Reference

FEATURES

APPLICATIONS

n 200mV Max Dropout at 10mA Output Current

n 4µA Typical Quiescent Current

n 0.15% Max Initial Accuracy

n No Output Capacitor Required

n Output Sources 10mA, Sinks 2mA

n 40ppm/°C Max Drift

n Voltage Options: 2.5V, 3V, 4.1V, 5V and Adjustable

n Battery-Powered Systems

n Handheld Instruments

n Precision Power Supplies

n A/D and D/A Converters

n Available in the SO-8 Package

LTC1798-2.5 Temperature Drift

LTC1798-2.5

OUT

GND

2.7V

TO 12.6V

62.5V

1798 TA01

0.1µF

TEMPERATURE (°C)

–40 –20 0 20 40 60 80 100

REFERENCE VOLTAGE CHANGE (mV)

1798 TA02

–2

–1

–3

–4

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

LTC1798 Series

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PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS

Operating Temperature Range...................... 0°C to 70°C

Extended Commercial Operating

Temperature Range .................................. –40°C to 85°C

Junction Temperature ........................................... 110°C

Storage Temperature Range ................... –65°C to 150°C

Lead Temperature (Soldering, 10 sec) .................. 300°C

(Note 1)

TOP VIEW

DNC*

OUT

DNC*

*DNC

**DNC/FB

GND

S8 PACKAGE

8-LEAD PLASTIC SO

TJMAX = 125°C, qJA = 190°C/W

* CONNECTED INTERNALLY. DO NOT CONNECT EXTERNAL CIRCUITRY TO THESE PINS

** DNC FOR LTC1798-2.5/LTC1798-3/LTC1798-4.1/LTC1798-5, FB FOR LTC1798

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE

LTC1798CS8#PBF (OBSOLETE) LTC1798CS8#TRPBF 1798 8-Lead Plastic SO 0°C to 70°C

LTC1798CS8-2.5#PBF LTC1798CS8-2.5#TRPBF 179825 8-Lead Plastic SO 0°C to 70°C

LTC1798CS8-3#PBF LTC1798CS8-3#TRPBF 17983 8-Lead Plastic SO 0°C to 70°C

LTC1798CS8-4.1#PBF LTC1798CS8-4.1#TRPBF 179841 8-Lead Plastic SO 0°C to 70°C

LTC1798CS8-5#PBF LTC1798CS8-5#TRPBF 17985 8-Lead Plastic SO 0°C to 70°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

AVAILABLE OPTIONS

OUTPUT VOLTAGE

(V)

TEMPERATURE

RANGE

(ºC)

ACCURACY

(%)

TEMPERATURE

COEFFICIENT

(PPM/ºC)

PACKAGE STYLE

SO-8 (S8)

ORDER NUMBER PART MARKING

2.5 0 to 70 0.15 40 LTC1798CS8-2.5 179825

3 0 to 70 0.15 40 LTC1798CS8-3 17983

4.096 0 to 70 0.15 40 LTC1798CS8-4.1 179841

5 0 to 70 0.15 40 LTC1798CS8-5 17985

Adjustable 0 to 70 0.4 40 LTC1798CS8 1798

LTC1798 Series

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ELECTRICAL CHARACTERISTICS

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The LTC1798 is guaranteed functional over the operating

temperature range of –40°C to 100°C.

Note 3: If the part is stored outside of the speciﬁed operating temperature

range, the output may shift due to hysteresis.

Note 4: ESD (Electostatic Discharge) sensitive device. Extensive use of

ESD protection devices are used internal to the LTC1798, however, high

electrostatic discharge can damage or degrade the device. Use proper ESD

handling precautions.

Note 5: Peak-to-peak noise is measured with a single pole highpass ﬁlter

at 0.1Hz and 2-pole lowpass ﬁlter at 10Hz.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VIN Input Voltage Range l12.6 V

IIN Input Current FB = OUT for LTC1798

4 6.5

8.5

µA

VOUT Output Voltage (Note 4) LTC1798, FB = OUT

LTC1798 ADJ

LTC1798-2.5

LTC1798-3

LTC1798-4.1

LTC1798-5

LTC1798 All Fixed Options

2.3755

–0.4

2.4963

2.9955

4.090

4.9925

–0.15

2.385

2.5

4.096

2.3945

0.4

2.5037

3.0045

4.102

5.0075

0.15

enOutput Voltage Noise (Note 5) 0.1Hz ≤ f ≤ 10Hz 8 ppmP-P

TC Output Voltage Temp Coefﬁcient (Note 6) TMIN ≤ TJ ≤ TMAX l15 40 ppm/°C

VOUT/VIN Line Regulation VIN = (VOUT(NOMINAL) + 0.2V) to 12.6V l30 120 ppm/V

VOUT/IOUT Load Regulation (Note 7) Sourcing 0mA to 10mA l0.1 0.3 mV/mA

Sinking 0mA to 2mA

1.75 4

6.5

mV/mA

ISC Short-Circuit Output Current VOUT Shorted to GND

VOUT Shorted to VIN

∆VDO Dropout Voltage (Note 8) IOUT = 0, ∆VOUT ≤ 0.1%

IOUT = 10mA, ∆VOUT ≤ 0.1%

100

200

VHYST Output Hysteresis (Note 9) ∆T = –40°C to 85°C

∆T = 0°C to 70°C

200

ppm

IFB FB Pin Input Current LTC1798, OUT = FB 10 nA

The l denotes speciﬁcations which apply over the full speciﬁed temperature

range, otherwise speciﬁcations are at TA = 25°C. VIN = VOUT(NOMINAL) + 0.2V, IOUT = 0mA unless otherwise noted. FB = OUT for the LTC1798.

Note 6: Temperature coefﬁcient is the change in output voltage divided by

the nominal output voltage divided by the speciﬁed temperature range.

Note 7: Load regulation is measured on a pulse basis from no load to the

speciﬁed load current. Output changes due to die temperature change

must be taken into account separately.

Note 8: Dropout voltage is (VIN – VOUT) when VOUT falls to 0.1% below its

nominal value at VIN = VOUT + 0.5V.

Note 9: Hysteresis in output voltage is created by package stress that

differs depending on whether the IC was previously at a higher or lower

temperature. Output voltage is always measured at 25°C, but the IC is

cycled hot or cold before successive measurements. Hysteresis is not

normally a problem for operational temperature excursions where the

instrument might be stored at high or low temperature.

LTC1798 Series

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TYPICAL PERFORMANCE CHARACTERISTICS

OUTPUT SOURCE CURRENT (mA)

DROPOUT VOLTAGE (mV)

100

00 1 10 100

1798 G01

0.1

TA = 25°C

TEMPERATURE (°C)

–50 –25

INPUT CURRENT (µA)

150

1798 G02

0 25 50 75 100 125

VIN = 2.7V

TEMPERATURE (°C)

–50 –25

OUTPUT SHORT-CIRCUIT CURRENT (mA)

150

1798 G03

0 25 50 75 100 125

TA = 25°C

VIN = VOUT(NOM) + 0.2V

OUTPUT

SHORTED

TO VIN

OUTPUT

SHORTED

TO GND

INPUT VOLTAGE (V)

OUTPUT SHORT-CIRCUIT CURRENT (mA)

46 8 10

1798 G04

12 14

TA = 25°C

OUTPUT SHORTED

TO VIN

INPUT VOLTAGE (V)

OUTPUT SHORT-CIRCUIT CURRENT (mA)

46 8 10

1798 G05

12 14

TA = 25°C

OUTPUT SHORTED

TO GND

OUTPUT CURRENT (mA)

∆VOUT FROM NO LOAD (mV)

–1

–2

–3

–4

–5 0 1 10 100

1798 G06

0.1

TA = 25°C

VIN = VOUT(NOM) + 0.2V

SINKING

SOURCING

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

2.5010

2.5005

2.5000

2.4995 46 8 10

1798 G07

12 14

TA = 25°C

INPUT VOLTAGE (V)

INPUT CURRENT (µA)

446 8 10

1798 G08

12 14

TA = 25°C

FREQUENCY (Hz)

POWER SUPPLY REJECTION RATIO (dB)

010 1k 10k

1798 G09

100

VIN = 2.7V

LTC1798-2.5* Output Short-Circuit

Current vs Input Voltage

LTC1798-2.5* Output Short-Circuit

Current vs Input Voltage

LTC1798 Series

Load Regulation

LTC1798-2.5*

Output Voltage vs Input Voltage

LTC1798-2.5*

Input Current vs Input Voltage

LTC1798-2.5

PSRR vs Frequency

LTC1798-2.5* Dropout Voltage

vs Output Source Current

LTC1798-2.5*

Input Current vs Temperature

LTC1798 Series Output Short-Circuit

Current vs Temperature

LTC1798 Series

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TYPICAL PERFORMANCE CHARACTERISTICS

5µV/DIV

1798 G10

1SEC/DIV

VIN = 2.7V

INPUT VOLTAGE (V)

012345678910

INPUT CURRENT (µA)

1798 G11

1400

1200

1000

800

600

400

200

TA = –55°C

TA = 25°C

TA = 125°C

INPUT VOLTAGE (V)

00.5 1 1.5 2 2.5 3 3.5 4 4.5 5

INPUT CURRENT (µA)

1798 G12

250

200

150

100

TA = 25°C

TA = –55°C

TA = 125°C

LTC1798-2.5

0.1Hz to 10Hz Noise

LTC1798-5 Input Current

vs Input Voltage in Dropout

LTC1798-2.5 Input Current

vs Input Voltage in Dropout

PIN FUNCTIONS

DNC (Pins 1, 5, 7, 8): Do Not Connect. Connected

internally for post package trim. These pins must be left

unconnected.

IN (Pin 2): Positive Supply. Bypassing with a 0.1µF capaci-

tor is recommended if the output loading changes. (VOUT

+ 0.2V) ≤ VIN ≤ 12.6V.

DNC (Pin 3): (LTC1798-2.5/LTC1798-3/LTC1798-4.1/

LTC1798-5) Do Not Connect. Connected internally for post

package trim. This pin must be left unconnected.

FB (Pin 3): (LTC1798) Resistor Divider Feedback Pin.

Connect a resistor divider from OUT to GND and the center

tap to FB. This pin sets the output potential.

OUT =+











2 385

R1 is connected from OUT

to FB and R2 from FB to GND. Selecting R2 ≥ 10k will

make IOUT < 250µA.

GND (Pin 4): Negative Supply or Ground Connection.

OUT (Pin 6): Reference Output. The output can source

up to 10mA and sink up to 2mA. It is stable with output

bypass capacitor ranging from 0µF to 1µF.

LTC1798 Series

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Figure 1. Reference Output Load Transient Response, 1µF Output Capacitor

10ms/DIV

VOUT

100mV/DIV

IOUT

1mA

0mA

1798 F01a

Longer Battery Life

Series references have an advantage over shunt style

references. To operate, shunt references require a resistor

between the power supply and the output. This resistor

must be chosen to supply the maximum current that is

demanded by the circuit being regulated. When the circuit

being controlled is not operating at this maximum current,

the shunt reference must always sink this current, resulting

in high power dissipation and short battery life.

The LTC1798 series low dropout references do not require

a current setting resistor and can operate with any supply

voltage from (VOUT(NOMINAL) + 0.2V) to 12.6V. When the

circuitry being regulated does not demand current, the

LTC1798 series reduces its dissipation and battery life is

extended. If the reference is not delivering load current it

BLOCK DIAGRAM

–

1798 BD

OUT

3 (LTC1798)FB

2.385V

GND

NOTE: R1 AND R2 ARE NOT CONNECTED FOR LTC1798

0.5ms/DIV

VOUT

100mV/DIV

IOUT

1mA

0mA

1798 F01b

APPLICATIONS INFORMATION

dissipates only 10.8µW when operating on a 2.7V supply

for LTC1798-2.5, yet the same connection can deliver

10mA of load current when demanded.

Output Bypass Capacitor

The LTC1798 series is designed to be stable with or without

capacitive loads. With no capacitive load, the reference

is ideal for fast settling applications, or where PC board

space is at a premium.

In applications with signiﬁcant output loading changes, an

output bypass capacitor of up to 1µF can be used to improve

the output transient response. Figure 1 shows the response

of the reference to a 1mA to 0µA load step with a 1µF output

capacitor. If more than 1µF of output capacitance is required,

a resistor in series with the capacitor is recommended

LTC1798 Series

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LTC1798-5

OUT

GND

5.2V

12.6V

65V

1798 F02

0.1µF

COUT

>1µF

DAMPING RESISTOR

<1k

APPLICATIONS INFORMATION

Figure 2. Adding a Damping Resistor with

Output Capacitors Greater Than 1µF

Figure 3. Damping Resistance vs Output Capacitor Value

OUTPUT CAPACITOR VALUE (µF)

RESISTOR VALUE (Ω)

100

10k

10 100 1000

1798 F03

These references consume only 4µA of quiescent current

under light and heavy loads as well as in dropout; whereas,

PNP-based references waste considerable amounts of cur-

rent when the pass transistor is saturated. In addition, the

LTC1798 series provides a lower dropout voltage (200mV

max) than PNP-based references.

to reduce the output ringing. Figure 2 illustrates the use of

a damping resistor for capacitive loads greater than 1µF.

Figure 3 shows the resistor and capacitor values required

to achieve critical damping.

Internal P-Channel Pass Transistor

The LTC1798 series features an internal P-channel MOSFET

pass transistor. This provides several advantages over

similar designs using a PNP bipolar pass transistor.

LTC1798 Series

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PACKAGE DESCRIPTION

Dimensions in inches (millimeters) unless otherwise noted.

S8 Package

8-Lead Plastic Small Outline (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1610)

.016 – .050

(0.406 – 1.270)

.010 – .020

(0.254 – 0.508)¥ 45∞

0– 8 TYP

.008 – .010

(0.203 – 0.254)

SO8 0303

.053 – .069

(1.346 – 1.752)

.014 – .019

(0.355 – 0.483)

TYP

.004 – .010

(0.101 – 0.254)

.050

(1.270)

BSC

1234

.150 – .157

(3.810 – 3.988)

NOTE 3

8765

.189 – .197

(4.801 – 5.004)

NOTE 3

.228 – .244

(5.791 – 6.197)

.245

MIN .160 .005

RECOMMENDED SOLDER PAD LAYOUT

.045 .005

.050 BSC

.030 .005

TYP

INCHES

(MILLIMETERS)

NOTE:

1. DIMENSIONS IN

2. DRAWING NOT TO SCALE

3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)

LTC1798 Series

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REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

C 9/10 Added Maximum limit for VIN in Electrical Characteristics section 3

(Revision history begins at Rev C)

LTC1798 Series

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Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

 LINEAR TECHNOLOGY CORPORATION 2008

LT 0910 REV C • PRINTED IN USA

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–

VSS = –4V

VOUT = –3V

0.2V ≤ VCC ≤ 8.5V

LTC1798-3

1/2 LTC1542

OUT

GND

1798 TA03

0.1µF

Micropower Low Dropout Negative Reference

LTC1798-2.5

OUT

GND

VCC = 5V 62.5V

VIRTUAL

GROUND

1798 TA04

0.1µF 0.1µF

Supply Splitter

LTC1798-3

LTC1096L

MPU

SERIAL DATA LINK

(MICROWIRE AND

SPI COMPATIBLE)

OUT

GND

CS/

SHDN

+IN

–IN

GND

VCC

CLK

DOUT

VREF

ANALOG INPUT

0V TO 3V RANGE

42VIN

3.2V TO

12.6V

1798 TA05

1µF

SERIAL DATA LINK

0.1µF

Low Power, Low Voltage Supply Reference for LTC1096L