LTC3201_15 Datasheet, PDF (4/8 Pages) Linear Technology – 100mA Ultralow Noise Charge Pump LED Supply with Output Current Adjust

LTC3201
PI FU CTIO S
V_OUT (Pin 1): Charge Pump Output. Bypass with a 1µF
ceramic capacitor to GND.
CP (Pin 2): Flying Capacitor Positive Terminal.
FILTER (Pin 3): Input Noise Filter Terminal. Bypass with a
0.22µF high resonant frequency ceramic capacitor to
GND. Place filter capacitor less than 1/8" from device.
CM (Pin 4): Flying Capacitor Negative Terminal.
GND (Pin 5): Ground. Connect to a ground plane for best
performance.
D0 (Pin 6): Current Control DAC LSB Input.
D1 (Pin 7): Current Control DAC Bit 1 Input.
D2 (Pin 8): Current Control DAC MSB Input. Inputs D0 to
D2 program a 3-bit DAC output which is used as the
internal reference voltage. The DAC output reference volt-
age is used to regulate amount of current flowing through
the LEDs. An internal control loop adjusts the charge
pump output such that the voltage drop across an external
sense resistor connected from FB to GND equals the
internal DAC output reference voltage. See Truth Table in
Applications Information section for internal reference
settings vs DAC code. When D0 to D2 are low, the part
enters a low current shutdown mode and the load is
disconnected from V_IN.
V_IN (Pin 9): Input Voltage. V_IN may be between 2.7V and
4.5V. Bypass V_IN with a 1µF low ESR capacitor to ground.
FB (Pin 10): Charge Pump Feedback Input. This pin acts
as a sense pin for I_OUT. Connect a sense resistor between
FB and GND to set the output current. I_OUT will be adjusted
until V_FB = internal DAC output reference.
SI PLIFIED BLOCK DIAGRA
4
V_OUT 1
FB 10
FILTER 3
LPF
V_IN 9
SOFT-START
AND
SWITCH CONTROL
1.8MHz
OSCILLATOR
CHARGE
PUMP
2 CP
1.2V
3-BIT
DAC
5
GND
4 CM
8 D2
7 D1
6 D0
3201 BD
3201f