LT3472
Boost and Inverting
DC/DC Converter
for CCD Bias
DESCRIPTIO
The LT
®
3472 dual channel switching regulator generates
positive and negative outputs for biasing CCD imagers.
The device delivers up to –8V at 50mA and 15V at 20mA
from a lithium-ion cell, providing bias for many popular
CCD imagers. Switching at 1.1MHz, the LT3472 uses tiny,
low profile capacitors and inductors and generates low
noise outputs that are easy to filter. Schottky diodes are
internal and the output voltages are set with one resistor
per channel, reducing external component count. The
entire solution is less than 1mm profile and occupies just
50mm
2
.
Internal sequencing circuitry disables the negative chan-
nel until the positive channel has reached 88% of its final
value, ensuring that the sum of the two outputs is always
positive. Separate soft-start capacitors for each output
allow the ramp of each output to be independently
controlled.
The LT3472 is available in a low profile (0.75mm) 10-pin
3mm
×
3mm DFN package.
FEATURES
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Generates 15V at 20mA, –8V at 50mA
from a Li-Ion Cell
Internal Schottky Diodes
V
IN
Range: 2.2V to 16V
Output Voltages Up to
±34V
Capacitor-Programmable Soft-Start
Sequencing: Positive Output Reaches 88% of Final
Value Before Negative Output Begins
Requires Only One Resistor to Set Output Voltage
Constant Switching Frequency Ensures Low
Noise Outputs
Available in a 10-Lead (3mm
×
3mm) DFN Package
APPLICATIO S
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CCD Bias
TFT LCD Bias
OLED Bias
±
Rail Generation for Op Amps
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
V
IN
3V TO 4.2V
22µH
47µH
Li-Ion CCD Bias Supply
Conversion Efficiency
2.2µF
1µF
80
75
POS CHANNEL
85
EFFICIENCY (%)
V
POS
15V
20mA
SWP
V
POS
550k
FBP
4.7pF
V
IN
SWN
DN
70
65
60
55
50
LT3472
320k
FBN
10pF
47µH
V
NEG
–8V
50mA
SHDN
SHDN
SSP
GND
100nF
SSN
100nF
2.2µF
45
40
0
10
30
20
LOAD CURRENT (mA)
40
50
2.2µF
3472 TA01a
U
U
U
NEG CHANNEL
3472 TA01b
3472f
1
LINER [ LINEAR TECHNOLOGY ]
