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February 2012
Rev. 2.1.0
Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001
GENERAL DESCRIPTION
The SP6669 is a synchronous current mode
PWM step down (buck) converter capable of
delivering up to 600mA of current. It features
a pulse skip mode (PSM) for light load
efficiency and a LDO mode for 100% duty
cycle.
With a 2.5V to 5.5V input voltage range and a
1.5MHz switching frequency, the SP6669
allows the use of small surface mount
inductors and capacitors ideal for battery
powered portable applications. The internal
synchronous switch increases efficiency and
eliminates the need for an external Schottky
diode. Low output voltages are easily
supported with the 0.6V feedback reference
voltage. The SP6669 is available in an
adjustable output voltage version, using an
external resistor divider circuit, as well as
fixed output voltage versions of 1.2V, 1.5V
and 1.8V.
Built-in over temperature and output over
voltage lock-out protections insure safe
operations under abnormal operating
conditions.
The SP6669 is offered in a RoHS compliant,
“green”/halogen free 5-pin SOT23 package.
APPLICATIONS
Portable Equipments
Battery Operated Equipments
Audio-Video Equipments
Networking & Telecom Equipments
FEATURES
Guaranteed 600mA Output Current
Input Voltage: 2.5V to 5.5V
1.5MHz PWM Current Mode Control
100% Duty Cycle LDO Mode Operations
Achieves 95% Efficiency
Fixed/Adjustable Output Voltage
Range
As Low as 0.6V with ±3% Accuracy
1.2V, 1.5V, 1.8V Fixed Voltage Options
Excellent Line/Load Transient
Response
200µA Quiescent Current
Over Temperature Protection
RoHS Compliant “Green”/Halogen Free
5-Pin SOT23 Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: SP6669 Application Diagram (Adj. version shown)
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© 2012 Exar Corporation 2/11 Rev. 2.1.0
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect
reliability.
Input Voltage VIN ....................................... -0.3V to 6.0V
Enable VFB Voltage ....................................... -0.3V to VIN
SW Voltage ...................................... -0.3V to (VIN+0.3V)
PMOS Switch Source Current (DC) ........................ 800mA
NMOS Switch Sink Current .................................. 800mA
Peak Switch Sink/Source Current ............................ 1.3A
Operating Junction Temperature1 .......................... 125°C
Storage Temperature .............................. -65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................... 240°C
ESD Rating (HBM - Human Body Model) .................... 2kV
ESD Rating (MM - Machine Model) ........................... 200V
OPERATING RATINGS
Input Voltage Range VIN ............................... 2.7V to 5.5V
Operating Temperature Range ................... -40°C to 85°C
Thermal Resistance θJA .....................................250°C/W
Thermal Resistance θJc ....................................... 90°C/W
Note 1: TJ is a function of the ambient temperature TA and
power dissipation PD (TJ= TA + PD x 250°C/W).
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Junction Temperature of TJ = 25°C only; limits applying over the full
Operating Junction Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test,
design, or statistical correlation. Typical values represent the most likely parametric norm at TA = 25°C, and are provided
for reference purposes only. Unless otherwise indicated, VIN = 3.6V.
Parameter
Min.
Typ.
Max.
Units
Conditions
Feedback Current IVFB
±30
nA
Regulated Feedback Voltage VFB
0.588
0.600
0.612
V
TA=25°C
Reference Voltage Line
Regulation ΔVFB
0.4
%/V
•
VIN=2.5V to 5.5V
Output Voltage Accuracy ΔVOUT%
-3
+3
%
•
Output Over-Voltage Lockout
ΔVOVL
20
50
80
mV
ΔVOVL = VOVL – VFB (Adj.)
2.5
7.8
13
%
ΔVOVL = VOVL – VOUT (Fixed)
Output Voltage Line Regulation
ΔVOUT
0.4
%/V
•
VIN=2.5V to 5.5V
Peak Inductor Current IPK
1.0
A
VIN=3V, VFB=0.5V or VOUT=90%, Duty
cycle <35%
Output Voltage Load Regulation
VLOADREG
0.5
%
Quiescent Current2 IQ
200
340
µA
VFB=0.5V or VOUT=90%
Shutdown Current ISHTDWN
0.1
1
µA
VEN=0V, VIN=4.2V
Oscillator Frequency fOSC
1.2
1.5
1.8
MHz
•
VFB=0.6V or VOUT=100%
290
Hz
•
VFB=0V or VOUT=0V
RDS(ON) of PMOS RPFET
0.45
0.55
Ω
ISW=100mA
RDS(ON) of NMOS RNFET
0.40
0.50
Ω
ISW=100mA
SW Leakage ILSW
±1
µA
VEN=0V, VSW=0V or 5V, VIN=5V
Enable Threshold VEN
1.2
V
•
Shutdown Threshold VEN
0.4
V
•
EN Leakage Current IEN
±1
µA
•
Note 1: The Switch Current Limit is related to the Duty Cycle. Please refer to figure 15 for details.
Note 2: Dynamic quiescent current is higher due to the gate charge being delivered at the switching frequency.
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© 2012 Exar Corporation 3/11 Rev. 2.1.0
BLOCK DIAGRAM
Fig. 2: SP6669 Block Diagram
PIN ASSIGNMENT
Fig. 3: SP6669 Pin Assignment
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© 2012 Exar Corporation 4/11 Rev. 2.1.0
PIN DESCRIPTION
Name
Pin Number
Description
EN
1
Enable Pin. Do not leave the pin floating.
VEN<0.4V: Shutdown mode
VEN>1.2V: Device enabled
GND
2
Ground Signal
SW
3
Switching Node
VIN
4
Power Supply Pin.
Must be decoupled to ground with a 4.7µF or greater ceramic capacitor.
VFB
5
Adjustable Version Feedback Input Pin.
Connect VFB to the center point of the resistor divider.
VOUT
Fixed Output Voltage Version, Output Voltage Pin.
An internal resistive divider divides the output voltage down for comparison to the
internal reference voltage.
ORDERING INFORMATION
Part Number
Temperature
Range
Marking
Package
Packing
Quantity
Note 1
Note 2
SP6669AEK-L/TRR3
-40°C≤TA≤+85°C
QBWW
SOT23-5
3K/Tape & Reel
Halogen Free
Adjustable
output voltage
SP6669BEK-L/TRR3
-40°C≤TA≤+85°C
RBWW
SOT23-5
3K/Tape & Reel
Halogen Free
1.2V fixed output
voltage
SP6669CEK-L/TRR3
-40°C≤TA≤+85°C
SBWW
SOT23-5
3K/Tape & Reel
Halogen Free
1.5V fixed output
voltage
SP6669DEK-L/TRR3
-40°C≤TA≤+85°C
TBWW
SOT23-5
3K/Tape & Reel
Halogen Free
1.8V fixed output
voltage
SP6669EB
SP6669 Evaluation Board
“YY” = Year – “WW” = Work Week – “X” = Lot Number; when applicable.
Note that the SP6669 series is packaged in Tape and Reel with a reverse part orientation as per the
following diagram
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© 2012 Exar Corporation 5/11 Rev. 2.1.0
TYPICAL PERFORMANCE CHARACTERISTICS
All data taken at VIN = 2.7V to 5.5V, TJ = TA = 25°C, unless otherwise specified - Schematic and BOM from Application
Information section of this datasheet.
Fig. 4: Efficiency vs Output Current (mA)
Fig. 5: Efficiency vs Output Current (mA)
Fig. 6: Efficiency vs Output Current (mA)
Fig. 7: Efficiency vs Output Current (mA)
Fig. 8: Output Voltage vs Load Current
Fig. 9: Reference Voltage vs Temperature
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© 2012 Exar Corporation 6/11 Rev. 2.1.0
Fig. 10: RDS(ON) vs Temperature
Fig. 11: RDS(ON) vs Input Voltage
Fig. 12: Dynamic Supply Current vs Temperature
Fig. 13: Dynamic Supply Current vs Supply Voltage
Fig. 14: Oscillator Frequency vs Temperature
Fig. 15: Oscillator Frequency vs Supply Voltage
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© 2012 Exar Corporation 7/11 Rev. 2.1.0
Fig. 16: Discontinuous Operation
Fig. 17: Start-up from Shutdown
Fig. 18: Load Step
Fig. 19: Load Step
Fig. 20: Load Step
Fig. 21: Load Step
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© 2012 Exar Corporation 8/11 Rev. 2.1.0
THEORY OF OPERATION
APPLICATIONS
The typical application circuit of the adjustable
output voltage option and the fixed output
voltage option are shown below.
Fig. 22: Adjustable Output Voltage Version
Fig. 23: Fixed Output Voltage Version
INDUCTOR SELECTION
Inductor ripple current and core saturation are
two factors considered to select the inductor
value.
Eq. 1:
IN
OUT
OUTLV
V
V
Lf
I1
1
Equation 1 shows the inductor ripple current
as a function of the frequency, inductance, VIN
and VOUT. It is recommended to set the ripple
current between 30% to 40% of the maximum
load current. A low ESR inductor is preferred.
CIN AND COUT SELECTION
A low ESR input capacitor can prevent large
voltage transients at VIN. The RMS current
rating of the input capacitor is required to be
larger than IRMS calculated by:
Eq. 2:
IN
OUTINOUT
OMAXRMS V
VVV
II
The ESR rating of the capacitor is an important
parameter to select COUT. The output ripple
VOUT is determined by:
Eq. 3:
OUT
LOUT Cf
ESRIV 81
Higher values, lower cost ceramic capacitors
are now available in smaller sizes. These
capacitors have high ripple currents, high
voltage ratings and low ESR that makes them
ideal for switching regulator applications. As
COUT does not affect the internal control loop
stability, its value can be optimized to balance
very low output ripple and circuit size. It is
recommended to use an X5R or X7R rated
capacitors which have the best temperature
and voltage characteristics of all the ceramics
for a given value and size.
OUTPUT VOLTAGE – ADJUSTABLE VERSION
The adjustable output voltage version is
determined by:
Eq. 4:
1
2
16.0 R
R
VVOUT
THERMAL CONSIDERATIONS
Although the SP6669 has an on board over
temperature circuitry, the total power
dissipation it can support is based on the
package thermal capabilities. The formula to
ensure safe operation is given in note 1.
PCB LAYOUT
The following PCB layout guidelines should be
taken into account to ensure proper operation
and performance of the SP6669:
1- The GND, SW and VIN traces should be kept
short, direct and wide.
2- VFB pin must be connected directly to the
feedback resistors. The resistor divider
network must be connected in parallel to the
COUT capacitor.
3- The input capacitor CIN must be kept as
close as possible to the VIN pin.
4- The SW and VFB nodes should be kept as
separate as possible to minize possible effects
from the high frequency and voltage swings of
the SW node.
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© 2012 Exar Corporation 9/11 Rev. 2.1.0
5- The ground plates of CIN and COUT should be
kept as close as possible.
OUPTUT VOLTAGE RIPPLE FOR VIN CLOSE TO
VOUT
When the input voltage VIN is close to the
output voltage VOUT, the SP6669 transitions
smoothly from the switching PWM converter
mode into a LDO mode. The following diagram
shows the output voltage ripple versus the
input voltage for a 3.3V output setting and a
200mA current load.
Fig. 24: VOUT Ripple Voltage
for VIN decreasing close to VOUT
DESIGN EXAMPLE
In a single Lithium-Ion battery powered
application, the VIN range is about 2.7V to
4.2V. The desired output voltage is 1.8V.
The inductor value needed can be calculated
using the following equation
IN
OUT
OUT
LV
V
V
If
L1
1
Substituting VOUT=1.8V, VIN=4.2V, ΔIL=180mA
to 240mA (30% to 40%) and f=1.3MHz gives
A 3.3µH inductor can be chosen with this
application. An inductor of greater value with
less equivalent series resistance would provide
better efficiency. The CIN capacitor requires
an RMS current rating of at least ILOAD(MAX)/2
and low ESR. In most cases, a ceramic
capacitor will satisfy this requirement.
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© 2012 Exar Corporation 10/11 Rev. 2.1.0
PACKAGE SPECIFICATION
5-PIN SOT23
Unit: mm
Symbol
Min.
Nom.
Max
A
0.90
1.30
1.40
A1
0.00
0.075
0.15
A2
0.90
1.20
1.25
b
0.30
-
0.50
c
0.08
-
0.20
D
2.80
2.90
3.00
E
2.60
2.80
3.00
E1
1.50
1.60
1.70
e
0.95 BSC
e1
1.90 BSC
L
0.30
0.45
0.60
L1
0.60 REF
L2
0.25 BSC
Θ
0
5
10
Θ1
3
5
7
Θ2
6
8
10
Note: JEDEC Outline MO-178 AA
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© 2012 Exar Corporation 11/11 Rev. 2.1.0
REVISION HISTORY
Revision
Date
Description
2.0.0
07/15/2011
Reformat of datasheet
Updated package specification
2.1.0
02/07/2012
Updated Typical Application schematics and Design example
FOR FURTHER ASSISTANCE
Email: customersupport@exar.com
Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx?
EXAR CORPORATION
HEADQUARTERS AND SALES OFFICES
48720 Kato Road
Fremont, CA 94538 – USA
Tel.: +1 (510) 668-7000
Fax: +1 (510) 668-7030
www.exar.com
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve
design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein,
conveys no license under any patent or other right, and makes no representation that the circuits are free of patent
infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a
user’s specific application. While the information in this publication has been carefully checked; no responsibility, however,
is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or
malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its
safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in
writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all
such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
