PCA9685 datasheet(29/52 Pages) PHILIPS

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PCA9685

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Product data sheet

Rev. 4 — 16 April 2015

29 of 52

NXP Semiconductors

PCA9685

16-channel, 12-bit PWM Fm+ I2C-bus LED controller

7.7 Using the PCA9685 with and without external drivers

The PCA9685 LED output drivers are 5.5 V only tolerant and can sink up to 25 mA at 5 V.

If the device needs to drive LEDs to a higher voltage and/or higher current, use of an

external driver is required.

• INVRT bit (MODE2 register) can be used to keep the LED PWM control firmware the

same independently of the type of external driver. This bit allows LED output polarity

inversion/non-inversion only when OE =0.

• OUTDRV bit (MODE2 register) allows minimizing the amount of external components

required to control the external driver (N-type or P-type device).

[1]

When OE = 1, LED output state is controlled only by OUTNE[1:0] bits (MODE2 register).

[2]

Correct configuration when LEDs directly connected to the LEDn outputs (connection to VDD through current limiting resistor).

[3]

Optimum configuration when external N-type (NPN, NMOS) driver used.

[4]

Optimum configuration when external P-type (PNP, PMOS) driver used.

Table 12.

Use of INVRT and OUTDRV based on connection to the LEDn outputs when OE =0[1]

INVRT OUTDRV Direct connection to LEDn

External N-type driver

External P-type driver

Firmware

External

pull-up

resistor

Firmware

External

pull-up

resistor

Firmware

External

pull-up

resistor

formulas and LED

output state values

inverted

LED current

limiting R[2]

formulas and LED

output state

values inverted

required

formulas and LED

output state values

apply

required

formulas and LED

output state values

inverted

LED current

limiting R[2]

formulas and LED

output state

values apply[3]

not

required[3]

formulas and LED

output state values

inverted

not required

formulas and LED

output state values

apply[2]

LED current

limiting R

formulas and LED

output state

values apply

required

formulas and LED

output state values

inverted

required

formulas and LED

output state values

apply[2]

LED current

limiting R

formulas and LED

output state

values inverted

not required formulas and LED

output state values

apply[4]

not

required[4]

INVRT = 0

OUTDRV = 1

INVRT = 1

OUTDRV = 1

INVRT = 1

OUTDRV = 0

Fig 13. External N-type driver

Fig 14. External P-type driver

Fig 15. Direct LED connection

LED0

+5 V

002aad169

LED0

+5 V

002aad170

LED0

+VDD

002aad171

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