SP6691
Micro Power Boost Regulator Series White LED Driver
FEATURES
•
Drives up to 6 LEDs @ 25mA
•
Drives up to 8 LEDs @ 20mA
•
High Output Voltage: Up to 30V
•
Optimized for Single Supply,
2.7V - 4.2V Applications
•
Operates Down to 1V
•
High Efficiency: Greater Than 75%
•
Low Quiescent Current: 20µA
•
Ultra Low Shutdown Current: 10nA
•
Single Battery Cell Operation
•
Programmable Output Voltage
•
1 switch (350mV at 350mA)
•
Lead Free, RoHS Compliant Packages:
8 Pin DFN, 5 Pin TSOT or 5 Pin SOT23
NC
FB
NC
SW
1
2
3
4
8
NC
SHDN
V
IN
GND
SP6691
8 Pin DFN
7
6
5
APPLICATIONS
•
White LED Driver
•
High Voltage Bias
•
Digital Cameras
•
Cell Phone
•
Battery Backup
•
Handheld Computers
DESCRIPTION
The SP6691 is a micro power boost regulator that is specifically designed for powering series
configuration white LED. The part utilizes fixed off time architecture and consumes only 10nA
quiescent current in shutdown. Low voltage operation, down to 1V, fully utilizes maximal battery
life. The SP6691 is offered in a 8 Pin DFN, 5-pin SOT-23 or 5 Pin TSOT package and enables
the construction of a complete regulator occupying < 0.2 in
2
board space.
TYPICAL APPLICATION CIRCUIT
10µH
2.7 to 4.2V
L1
D1
SW
V
IN
SP6691
SHDN
C2
FB
2.2
µF
4.7µF
C1
GND
R
b
Apr08-08 Rev E
Micro Power Boost Regulator Series White LED Driver
© 2008 Exar Corporation
1
ABSOLUTE MAXIMUM RATINGS
V
IN
....................................................................... 15V
SW Voltage .............................................. -0.4 to 30V
FB Voltage ......................................................... 2.5V
All other pins ................................... -0.3 to V
IN
+ 0.3V
Current into FB .................................................
±1mA
T
J
Max ............................................................. 125°C
Operating Temperature Range ............ -40°C to 85°C
Peak Output Current < 10us SW .................... 500mA
Specifications are at T
A
= 25°C, V
IN
= 3.3, V
SHDN
= V
IN
,
temperature range, unless otherwise specified.
PARAMETER
Input Voltage
Supply Current
Storage Temperature ...................... -65°C to +150°C
Power Dissipation. ......................................... 200mW
ESD Rating ................................................. 2kV HBM
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.
denotes the specifications which apply over the full operating
TYP
MAX
13.5
20
0.01
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
Q
MIN
1.0
UNITS
V
µA
µA
V
mV
CONDITIONS
30
1
1.27
No Switching
SHDN = 0V (off)
Reference Voltage
FB Hysteresis
V
FB
Input Bias Current
Line Regulation
Switch Off Time
Switch Saturation Voltage
Switch Current Limit
SHDN Bias Current
SHDN High Threshold (on)
SHDN Low Threshold (off)
Switch Leakage Current
V
FB
HYST
I
FB
V
o
/ V
I
T
OFF
V
CESAT
I
LIM
I
SHDN
V
IH
V
IL
I
SWLK
1.17
1.22
8
15
0.1
250
170
80
0.3
nA
%/V
nS
V
FB
= 1.22V
1.2
V
IN
13.5V
450
575
12
mV
mA
µA
V
I
SW
= 325mA
325
450
5
V
SHDN
= 3.3V
0.9
0.25
0.01
5
V
µA
Switch Off, V
SW
= 5V
PIN DESCRIPTION
PIN NUMBER
1
2
3
3
5
6
7
8
PIN NAME
NC
FB
NC
SW
GND
V
IN
SHDN
NC
8 PIN DFN DESCRIPTION
No connect.
Feedback.
No connect.
Switch input to the internal power switch
Ground
Input Voltage. Bypass this pin with a capacitor as close to the device
as possible.
Shutdown. Pull high (on) to enable. Pull low (off) for shutdown.
No connect.
Apr08-08 Rev E
Micro Power Boost Regulator Series White LED Driver
©2008 Exar Corporation
2
PIN DESCRIPTION
PIN NUMBER
1
2
3
4
5
PIN NAME
SW
GND
FB
SHDN
V
IN
DESCRIPTION
Switch input to the internal power switch.
Ground
Feedback
Shutdown. Pull high (on) to enable. Pull low (off) for shutdown.
Input Voltage. Bypass this pin with a capacitor as close to the device
as possible.
FUNCTIONAL DIAGRAM
5
VIN
SW
1
R1
R2
Q1
FB
Q2
+
-
X1
DISABLE
SET
250ns
ONE-SHOT
POWER
TRANSISTOR
3
R3
CLEAR
X2
DRIVER
+
-
R4
GND
SHDN
4
Shutdown
Logic
2
THEORY OF OPERATION
Operation can be best understood by referring to
the functional diagram above and the typical
application circuit in the front page. Q1 and Q2
along with R3 and R4 form a band gap refer-
ence. The input to this circuit completes a feed-
back path from the high voltage output through
a voltage divider, and is used as the regulation
control input. When the voltage at the FB pin is
slightly above 1.22V, comparator X1 disables
most of the internal circuitry. Current is then
provided by capacitor C2, which slowly dis-
charges until the voltage at the FB pin drops
below the lower hysteresis point of X1, about
6mV. X1 then enables the internal circuitry,
turns on chip power, and the current in the
inductor begins to ramp up. When the current
through the driver transistor reaches about
Apr08-08 Rev E
450mA, comparator X2 clears the latch, which
turns off the driver transistor for a preset 250nS.
At the instant of shutoff, inductor current is
diverted to the output through diode D1. During
this 250nS time limit, inductor current decreases
while its energy charges C2.
At the end of the 250ns time period, driver
transistor is again allowed to turn on which
ramps the current back up to the 450mA level.
Comparator X2 clears the latch, it’s output turns
off the driver transistor, and this allows delivery
of L1’s stored kinetic energy to C2. This switch-
ing action continues until the output capacitor
voltage is charged to the point where FB is at
band gap (1.22V). When this condition is
reached, X1 turns off the internal circuitry and
the cycle repeats.
©2008 Exar Corporation
Micro Power Boost Regulator Series White LED Driver
3
Refer to the typical application circuit, T
AMB
= 25°C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
90
80
70
60
50
0
20
40
Vout = 12V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
13.0
12.5
Vout (V)
Vout = 12V Load Regulation
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
Efficiency (%)
12.0
11.5
11.0
0
20
40
60
80
100
120
140
160
Iout (mA)
60
80
Iout (mA)
100
120
140
160
Figure 1. 12V Output Efficiency
Figure 2. 12V Output Load Regulation
90
Vout = 15V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3.3V
Vi
16.0
Vout = 15V Load Regulation
Vin = 5.0V
Vin = 4.2V
Vin = 3.3V
Vin = 2.7V
Efficiency (%)
80
15.5
70
Vout (V)
15.0
60
14.5
50
0
20
40
60
80
100
120
14.0
0
20
40
60
80
100
120
Iout (mA)
Iout (mA)
Figure 3. 15V Output Efficiency
Figure 4. 15V Output Load Regulation
90
80
70
60
50
0
20
Vout = 18V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
19.0
18.5
Vout (V)
Vout = 18V Load Regulation
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
Efficiency (%)
18.0
17.5
17.0
40
60
Iout (mA)
80
100
0
20
40
60
Iout (mA)
80
100
Figure 5. 18V Output Efficiency
Apr08-08 Rev E
Figure 6. 18V Output Load Regulation
Micro Power Boost Regulator Series White LED Driver
©2008 Exar Corporation
4
Refer to the typical application circuit, T
AMB
= 25°C, unless otherwise specified.
PERFORMANCE CHARACTERISTICS
90
Vout = 21V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
22.0
Vout = 21V Load Regulation
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
Efficiency (%)
80
21.5
Vout (V)
70
21.0
60
20.5
50
0
10
20
30
40
Iout (mA)
50
60
70
20.0
0
10
20
30
40
Iout (mA)
50
60
70
Figure 7. 21V Output Efficiency
Figure 8. 21V Output Load Regulation
90
Efficiency (%)
Vout = 24V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
25.0
Vout = 24V Load Regulation
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
80
70
60
50
0
10
20
30
Iout (mA)
40
50
60
24.5
Vout (V)
24.0
23.5
23.0
0
10
20
30
Iout (mA)
40
50
60
Figure 9. 24V Output Efficiency
Figure 10. 24V Output Load Regulation
90
80
Efficiency (%)
Vout = 30V Efficiency
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
31.0
30.5
Vout (V)
Vout = 30V Load Regulation
Vin =
5.0V
Vin =
4.2V
Vin =
3 3V
70
60
50
40
0
5
10
15
Iout (mA)
20
25
30
30.0
29.5
29.0
0
5
10
15
Iout (mA)
20
25
30
Figure 11. 30V Output Efficiency
Apr08-08 Rev E
Figure 12. 30V Output Load Regulation
©2008 Exar Corporation
Micro Power Boost Regulator Series White LED Driver
5
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