SP7648
Low Reference High Efficiency Boost Regulator
November 2012
Rev. 2.0.0
GENERAL DESCRIPTION
The SP7648 is an ultra-low quiescent current,
high efficiency step-up DC-DC converter ideal
for single cell Li-Ion or dual cell alkaline
battery applications to drive various LEDs. The
SP7648 combines low quiescent current and
excellent light-load efficiency of PFM control.
The SP7648 features synchronous rectification,
a 0.3Ω charging switch, an anti-ringing
inductor switch, under-voltage lockout and
programmable inductor peak current. The
device can be shut down by a 1nA active LOW
shutdown pin. A very low 0.288V reference
voltage is optimized for driving a constant
current load.
APPLICATIONS
LED Driver
Camera Flash
Handheld Portable Devices
FEATURES
True Shutdown
700mA Output Current at 3.3V Input;
4.2V output
92% Efficiency from 2.7V
IN
to 3.3V
OUT
2.7V to 4.5V Wide Input Voltage Range
5V Fixed or Adjustable Output
0.3Ω Switch
Integrated Synchronous Rectifier:0.3Ω
Anti-Ringing Switch Technology
Programmable Inductor Peak Current
Logic Shutdown Control
Low 0.8V or 0.288V Reference Voltage
Small 10-pin DFN and MSOP Package
TYPICAL APPLICATION DIAGRAM
Fig. 1: SP7648 Application Diagram
Exar Corporation
48720 Kato Road, Fremont CA 94538, USA
www.exar.com
Tel. +1 510 668-7000 – Fax. +1 510 668-7001
SP7648
Low Reference High Efficiency Boost Regulator
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.
LX, Vo, V
BATT
, FLASHOUT, FB to GND pin ......... -0.3 to 6.0V
SHDN, FLASH................................... -0.3V to V
BATT
+1.0V
VO, GND, LX Current ................................................ 2A
Reverse V
BATT
Current .......................................... 220mA
Forward V
BATT
Current.......................................... 500mA
Storage Temperature .............................. -65°C to 150°C
ESD Rating (HBM - Human Body Model) .................. 1.5kV
OPERATING RATINGS
Input Voltage Range V
BATT
............................ 2.7V to 4.5V
Ambient Temperature Range ................... -40°C to +85°C
Thermal Resistance ......................................................
θ
JA
(DFN-10) ............................................... 40.5°C/W
θ
JA
(MSOP-10) .......................................... 214.0°C/W
ELECTRICAL SPECIFICATIONS
Specifications with standard type are for an Operating Ambient Temperature of T
A
= 27°C only; limits applying over the full
Operating Ambient 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 T
A
= 27°C, and are provided
for reference purposes only. Unless otherwise indicated, V
BATT
= V
SHDN
= 3.6V, V
FB
= ZeroV, I
LOAD
= 0mA, V
OUT
= 5.0V,
T
A
= –40°C to 85°C.
Parameter
Input Voltage Operating Range
V
BATT
Output Voltage Range V
OUT
Min.
2.7
27
0.5
4.6
-
-
650
Typ.
-
-
0.61
5.0
1
250
92
800
1600
800
Output Current (Note 2)
Minimum Off-Time Constant K
OFF
Maximum On-Time Constant K
ON
Enable Valid to Output Stable
(Note 3)
NMOS Switch Resistance
PMOS Switch Resistance
FB Set Voltage, V
FB
FB Input Current
SHDN Input Voltage V
IL
(Note 1)
SHDN Input Voltage V
IH
(Note 1)
SHDN Input Current
LX Pin Leakage
FLASH Threshold V
IL
Max.
4.5
5.5
0.7
5.4
500
750
-
1000
Units
V
V
V
V
nA
nA
%
mA
•
•
•
•
•
•
•
Conditions
After Startup
Under Voltage Lock-out UVLO
Output Voltage V
O
Shutdown Current into V
O
, I
SDO
Shutdown Current into V
BATT
, I
SDB
Efficiency
Inductor Peak Current Limit, I
PK
Internal Feedback Divider
V
SHDN
= ZeroV
V
SHDN
= ZeroV, V
BATT
= 2.7V
V
BATT
= 2.7V, I
OUT
= 200mA, R
LIM
= 2kΩ
R
LIM
= 2kΩ, I
PK
= 1600/R
LIM
R
LIM
= 1kΩ, I
PK
= 1600/R
LIM
V
BATT
= 2.7V, R
LIM
=1kΩ
V
BATT
= 2.7V, R
LIM
=2kΩ
V
BATT
= 2.7V, R
LIM
= 4kΩ
K
OFF
≤T
OFF
(V
OUT
- V
BATT
)
K
ON
≥T
ON
(V
BATT
)
I
LOAD
= 1mA
400
200
0.5
2.0
1.0
3.5
300
0.30
0.30
0.76
0.266
-
2.0
1
100
3
0.4
1.0
0.8
0.288
1
1.5
5.0
500
0.6
0.6
0.84
0.310
100
0.5
mA
V*µs
V*µs
µs
Ω
Ω
V
nA
V
nA
µA
V
•
•
•
•
•
•
•
•
•
I
NMOS
= 100mA
I
PMOS
= 100mA
External feedback Flash = 0
External feedback Flash = 1
V
FB
=1.3V
V
BATT
= 2.7V
FLASH Threshold V
IH
Note 1: SHDN must transition faster than 1V/100mS for proper operation.
Note 2: Output Current I = (VIN/VOUT) x Efficiency x (Inductor Peak Current - Inductor Ripple Current)/2
© 2012 Exar Corporation
2/13
Rev. 2.0.0
SP7648
Low Reference High Efficiency Boost Regulator
Note 3: Guaranteed by Design.
BLOCK DIAGRAM
Fig. 2: SP7648 Block Diagram
PIN ASSIGNMENT
Fig. 3: SP7648 Pin Assignment
© 2012 Exar Corporation
3/13
Rev. 2.0.0
SP7648
Low Reference High Efficiency Boost Regulator
PIN DESCRIPTION
Name
V
BATT
Pin Number
1
Description
Battery Voltage.
The startup circuitry is powered by this pin. Battery Voltage is used to calculate switch
off time: T
OFF
= K
OFF
/ (V
OUT
-V
BATT
). When the battery voltage drops below 0.61V the
SP7648goes into an undervoltage lockout mode (UVLO), where the part is shutdown.
Reference Control Input.
Internal Reference defaults to 0.8V if FLASH= LOW and 0.288V if FLASH = HIGH.
No connection.
This pin is bonded out for test purposes only and must be left floating in all applications.
Current Limit Resistor.
By connecting a resistor R
LIM
from this pin t ground the inductor peak current is set by
I
PEAK
=1600/R
LIM
. The range for R
LIM
is 9kΩ (for 180mA) to 1KΩ (for 1.6A).
Shutdown Not.
Tie this pin high to V
BATT
, for normal operation. Pull this pin to ground to disable all
circuitry inside the chip.
Feedback.
Connect this pin to GND for fixed +5V operation. Connect this pin to a resistor voltage
divider between V
OUT
and GND for adjustable output operation.
Ground.
Connect to ground plane.
Power Ground.
The inductor charging current flows out of this pin.
Inductor Switching Node.
Connect one terminal of the inductor to the positive terminal of the battery. Connect
the second terminal of the inductor to this pin. The inductor charging current flows into
LX, through the internal charging N-channel FET, and out the PGND pin.
Output Voltage.
The inductor current flows out of this pin during switch off-time. It is also used as the
internal regulator voltage supply. Connect this pin to the positive terminal of the output
capacitor.
Connect to ground signal.
FLASH
NC (Test)
R
LIM
2
3
4
SHDN
5
FB
GND
PGND
6
7
8
LX
9
V
OUT
GND
10
Thermal Pad
ORDERING INFORMATION
Part Number
SP7648ER-L
SP7648ER-L/TR
SP7648EU-L
SP7648EU-L/TR
Ambient
Temperature
Range
-40°C≤T
A
≤+85°C
-40°C≤T
A
≤+85°C
Marking
SP76
48ER
WWX
7648
EXXX
YWW
Package
Packing
Quantity
Bulk
3K/Tape & Reel
Bulk
2.5K/Tape & Reel
Note 1
Note 2
DFN-10
MSOP-10
“YY” = Year – “WW” = Work Week – “X” = Lot Number; when applicable.
© 2012 Exar Corporation
4/13
Rev. 2.0.0
SP7648
Low Reference High Efficiency Boost Regulator
TYPICAL PERFORMANCE CHARACTERISTICS
Fig. 4: Output Current versus Input Voltage
Fig. 5: Efficiency versus Input Voltage
Fig. 6: Output Current versus Input Voltage
Fig. 7: Efficiency versus Input Voltage
Fig. 8: Output Current versus Input Voltage
Fig. 9: Efficiency versus Input Voltage
© 2012 Exar Corporation
5/13
Rev. 2.0.0
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