LT3472_15 Datasheet, PDF (1/12 Pages) Linear Technology – Boost and Inverting DC/DC Converter for CCD Bias

FEATURES
■ _{Generates 15V at 20mA, –8V at 50mA}
from a Li-Ion Cell
■ _{Internal Schottky Diodes}
■ _{VIN 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}
U
APPLICATIO S
■ _{CCD Bias}
■ _{TFT LCD Bias}
■ _{OLED Bias}
■ _{± Rail Generation for Op Amps}
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
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
50mm².
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.
Li-Ion CCD Bias Supply
V_IN
3V TO 4.2V
22µH
47µH
2.2µF
1µF
V_POS
15V
20mA
550k
4.7pF
SWP
V_POS
FBP
V_IN
LT3472
SHDN
2.2µF
SHDN
SSP
GND
100nF
SWN
DN
FBN
320k
10pF
47µH
V_NEG
–8V
50mA
SSN
100nF
2.2µF
3472 TA01a
Conversion Efficiency
85
80
POS CHANNEL
75
70
NEG CHANNEL
65
60
55
50
45
40
0
10
20
30
40
50
LOAD CURRENT (mA)
3472 TA01b
3472f
1