LP8501 datasheet(19/51 Pages) TI1

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LP8501

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SNVS548D – SEPTEMBER 2008 – REVISED AUGUST 2013

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When the LP8501 is shut down (through chip_en), the fading off can be achieved. When “fade-to-off” bit

(in register 36h) is set to 1, the group fade times have effect, and the LEDs fade off according to the time

set in the register.

Examples of Controlling LED Drivers

1. Direct PWM Control Example —Start up the device:

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Supply, e.g., 3.6V to VDD.

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Supply, e.g., 1.8V to EN.

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Write 40h (0100 0000b) to address 00h (enable LP8501).

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Wait 500 µs (startup delay).

Check LED powering

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Suppose LED outputs from 1 to 6 are connected to VDD and LED outputs 7 to 9 are connected to VOUT.

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Write 01h (0000 0001b) to address 05h (VDD1_6 powered from VDD and VDD7_9 powered from VOUT.

Enable charge pump to AUTO mode and use internal clock

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Write 19h (0001 1001b) to address 36h.

Write PWM values:

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Write 80h (1000 0000b) to address 16h (LED output 1 PWM duty cycle to 50%).

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Write C0h (1100 0000b) to address 1Ah (LED output 5 PWM duty cycle to 75%).

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Write FFh (1111 1111b) to address 1Eh (LED output 9 PWM duty cycle to 100%).

LED outputs are turned on after PWM values are written. Changes to the PWM value registers are reflected

immediately to the LED brightness. Default LED output current (17.5 mA) is used for LED outputs, if no other

values are written.

2. Controlling by Program Execution Engines Example —Start up device and configure device to SRAM

write mode:

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Supply e.g. 3.6V to VDD.

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Supply e.g. 1.8V to EN.

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Generate 32 kHz clock signal to CLK pin.

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Write 40h (0100 0000b) to address 00h.

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Wait 500 µs (startup delay).

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Write 14h (0001 0100b) to address 01h (configure engines 1 and 2 to Load mode).

Check LED powering

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Suppose LED outputs from 1 to 6 are connected to VOUT and LED outputs 7 to 9 are connected to VDD.

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Write 02h (0000 0010b) to address 05h (VDD1_6 powered from VOUT and VDD7_9 powered from VDD.

Program load to SRAM

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Write 00h (0000 0000b) to register 4Fh (select memory page 0).

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Write 9Dh (1001 1101b) to register 50h (select LED output 1 for engine 1 MSB, instruction part).

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Write 01h (0000 0001b) to register 51h (select LED output 1 for engine 1 LSB, output selection part).

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Write 40h (0100 0000b) to register 52h (set PWM value to full FFh MSB, instruction part).

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Write FFh (1111 1111b) to register 53h (set PWM value to full FFh LSB, PWM value part).

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Write 7Eh (0111 1110b) to register 54h (wait for 0.48s (maximum) MSB, instruction part).

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Write 00h (0000 0000b) to register 55h (wait for 0.48s LSB).

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Write 40h (0100 0000b) to register 56h (set PWM value to zero MSB, instruction part).

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Write 00h (0000 0000b) to register 57h (set PWM value to zero LSB, PWM value part).

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Write 7Eh (0111 1110b) to register 58h (wait for 0.48s MSB, instruction part).

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Write 00h (0000 0000b) to register 59h (wait for 0.48s LSB).

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Write A2h (1010 0010b) to register 5Ah (branch instruction with loop count 4 MSB, instruction part).

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Write 01h (0000 0001b) to register 5Bh (branch instruction with loop count 4 LSB sets program counter

value to '1', i.e., program continues execution in this case from setting PWM value).

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Write C0h (1100 0000b) to register 5Ch (end instruction MSB, instruction part).

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Write 00h (0000 0000b) to register 5Dh (end instruction LSB).

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Write 9Dh (1001 1101b) to register 5Eh (select LED output 3 for engine 2MSB, instruction part).

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