LT3487_15 Datasheet, PDF (1/16 Pages) Linear Technology – Boost and Inverting Switching Regulator for CCD Bias

FEATURES
■ _{Generates 15V at 45mA, –8V at 90mA from a}
Li-Ion Cell
■ _{Output Disconnect}
■ _{Sequencing: Positive Output Reaches Regulation}
Before Negative Channel Begins Switching
■ _{Internal Schottky Diodes}
■ _{2MHz Constant Switching Frequency}
■ _{Requires Only One Resistor per Channel to Set}
Output Voltages
■ _{VIN Range: 2.3V to 16V}
■ _{Output Voltage Up to 28V}
■ _{Short-Circuit Robust}
■ _{Capacitor Programmable Soft-Start}
■ _{Separate VBAT Pin Allows Separate Sources for}
Power and Control Circuitry
■ _{Available in 10-Lead (3mm × 3mm) DFN Package}
U
APPLICATIO S
■ _{CCD Bias}
■ _{TFT LCD Bias}
■ _{OLED Bias}
■ _{±Rail Generation for Op Amps}
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
LT3487
Boost and Inverting
Switching Regulator
for CCD Bias
DESCRIPTIO
The LT^®3487 dual channel switching regulator generates
positive and negative outputs for biasing CCD imagers.
The device delivers up to –8V at 90mA and 15V at 45mA
from a lithium-ion cell, providing bias for many popular
CCD imagers. The boost regulator incorporates output
disconnect technology to eliminate the DC current path
from V_IN to the output load that is present in standard
boost configurations. The 2MHz switching frequency
allows CCD solutions using 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
the external component count.
Intelligent soft-start allows sequential soft-start of the two
channels with a single capacitor. The soft-start is sequenced
such that the output ramp of the negative channel begins
after the ramp of the positive channel. Internal sequencing
circuitry also disables the negative channel until the positive
channel has reached 87% of its final value, ensuring that
the sum of the two outputs is always positive.
The LT3487 is available in a 10-pin 3mm × 3mm DFN
package.
TYPICAL APPLICATIO
V_IN
3V TO 12V
2.2µF
1µF
47pF
15µH
V_NEG
–8V
90mA
324k
RUN/SS
22µF
100nF
15µH
10µH
SWN
V_IN
DN
V_BAT
LT3487
SWP
CAP
FBP
FBN
RUN/SS
GND
V_POS
549k
100nF
4.7µF
3487 TA01a
V_POS
15V
45mA
Conversion Efficiency
80
POS CHANNEL AT CAP
75
70
POS CHANNEL
65
AT V_POS
60
NEG CHANNEL
55
50
45
40
0
V_IN = 3.6V
20
40
60
80 100
LOAD CURRENT (mA)
3487 TA01b
3487f
1