LTC3217_15 Datasheet, PDF (5/12 Pages) Linear Technology – 600mA Low Noise Multi-LED Camera Light Charge Pumps

LTC3217
TYPICAL PERFORMANCE CHARACTERISTICS T_A = 25°C unless otherwise noted.
1.5x Mode CPO Voltage
vs Load Current
4.8
C2 = C3 = C4 = 2.2μF
4.6
3.4V
4.4
3.5V
3.6V
4.2
3.3V
4.0
3.2V
3.8
3.6
0
3.1V
V_BAT = 3V
100 200 300 400 500
LOAD CURRENT (mA)
3217 G13
2x Mode CPO Voltage
vs Load Current
5.2
C2 = C3 = C4 = 2.2μF
5.1
5.0
3.6V
4.9
4.8
3.3V
4.7
3.2V
4.6
3.1V
4.5
V_BAT = 3V
4.4
4.3
4.2
0
100 200 300 400 500
LOAD CURRENT (mA)
3217 G14
PIN FUNCTIONS
C1P, C2P, C1M, C2M (Pins 1, 16, 14, 12): Charge Pump
Flying Capacitor Pins. A 2.2μF X7R or X5R ceramic capacitor
should be connected from C1P to C1M and C2P to C2M.
CPO (Pin 2): Output of the charge pump used to power
all LEDs. This pin is enabled or disabled using the EN1
and EN2 inputs. A 2.2μF X5R or X7R ceramic capacitor
should be connected to ground.
EN1, EN2 (Pins 3, 11): Inputs. The EN1 and EN2 pins are
used to select which current level is being supplied to the
LEDs, as well as to put the part into shutdown mode. The
truth table for these pins is as follows:
Truth Table
EN1
0
1
0
1
EN2
MODE
0
Shutdown
0
Low Current
1
High Current
1
Low + High Current
EN2 can be used for PWM of the LED currents. For proper
operation, the minimum pulse width should be 50μs and
the maximum low time should be 1ms if EN1 is low. If EN1
is high then the 1ms low time limitation does not apply.
LED1, LED2, LED3, LED4 (Pins 4, 5, 6, 7): LED1 to LED4
are the current source outputs. Each LED is connected
in between CPO (anodes) and LED1 – 4 (cathodes). The
current to each LED output is set via the EN1 and EN2
inputs, and the programming resistors connected from
I_SET1 and I_SET2 to GND. With the LTC3217, any of the four
LED outputs can be disabled by connecting the output
directly to CPO. 10μA of current will flow through each
directly connected LED output. For single LED applications,
all four LED pins may be tied together and will accurately
share current.
GND2 (Pin 8): Analog Ground. This pin should be con-
nected directly to a low impedance ground plane.
I_SET1/I_SET2 (Pins 9, 10): LED Current Programming Re-
sistor Pins. The I_SET1 and I_SET2 pins will servo to 1.22V.
Resistors connected between each of these pins and
GND are used to set the high and low LED current levels.
Connecting a resistor 2k or less will cause the LTC3217
to enter overcurrent shutdown.
GND1 (Pin 13): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
V_BAT (Pin 15): Supply Voltage. This pin should be bypassed
with a 2.2μF, or greater low ESR ceramic capacitor.
Exposed Pad (Pin 17): This pad should be connected
directly to a low impedance ground plane for optimal
thermal and electrical performance.
3217fa
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