LTC3217

5

3217f

PI FU CTIO S

1.5x Mode CPO Voltage

vs Load Current

LOAD CURRENT (mA)

3.6

4.0

4.4

4.8

3.8

4.2

4.6

100

200

300

400

3217 G13

500

0

C2 = C3 = C4 = 2.2

µF

3.2V

3.3V

3.6V

3.1V

3.5V

3.4V

2x Mode CPO Voltage

vs Load Current

LOAD CURRENT (mA)

0

4.8

5.0

5.2

400

3217 G14

4.6

4.4

4.7

4.9

5.1

4.5

4.3

4.2

100

200

300

500

C2 = C3 = C4 = 2.2

µF

3.1V

3.2V

3.3V

3.6V

C1P, C2P, C1M, C2M (Pins 1, 16, 14, 12): Charge Pump

Flying Capacitor Pins. A 2.2

µFX7RorX5Rceramiccapaci-

tor 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 2.2

µF 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

EN2

MODE

0

0

Shutdown

1

0

Low Current

0

1

High Current

1

1

Low + High Current

EN2 can be used for PWM of the LED currents. For proper

operation, the minimum pulse width should be 50

µs 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

be disabled by connecting the output directly to CPO.

10

µA 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

connected directly to a low impedance ground plane.

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 over-current shutdown.

GND1 (Pin 13): Charge Pump Ground. This pin should be

connected directly to a low impedance ground plane.

bypassed with a 2.2

µF, 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.