Description

      The AT9530 is a 2-bit l2C-bus and SMBus I/O expander optimized for dimming LEDs in256 discrete steps for Red/Green/Blue (RGB) color mixing and backlight applications.

      The AT9530 contains an internal oscillator with two user programmable blink rates and duty cycles coupied to the output PWM. The LED brightness is controlled by setting the blink rate high enough (> 100 Hz) that the blinking cannot be seen and then using the duty cycle to vary the amount of time the LED is on and thus the average current through the LED.

      The initial setup sequence programs the two blink rates/duty cycles for each individual PWM. From then on, only one command from the bus master is required to turn individual LEDs ON, OFF, BLINK RATE 1 or BLINK RATE 2. Based on the programmed frequency and duty cycle, BLINK RATE 1 and BLINK RATE 2 will cause the LEDs to appear at a different brightness or blink at periods up to 1.69 second. The open-drain outputs directly drive the LEDs with maximum output sink current of 25 mA per bit and 50 m A per package.

     To blink LEDs at periods greater than 1.69 second, the bus master (MCU, MPU, DSP,chip set, etc.) must send repeated commands to turn the LED on and off as is currently done when using normal I/O Expanders like the AT8574 or AT9554. Any bits not used for controlling the LEDs can be used for General Purpose parallel Input/Output (GPIO) expansion which provides a simple solution when additional I/O is needed for ACPI power switches, sensors, push buttons, alarm monitoring, fans,etc.

     The active LOW hardware reset pin (RESET) and Power-On Reset (POR) initialize the registers to their default state causing the bits to be set HIGH (LED off).

     One hardware address pin on the AT9530 allows two devices to operate on the same bus.

Features

• 2 LED drivers (on, off, flashing at a programmable rate)

• 2 selectable, fully programmable blink rates (frequency and duty cycle) between 0.591 Hz and 152 Hz (1.69 seconds and 6. 58 milliseconds)

• 256 brightness steps

• Input/output not used as LED drivers can be used as regular GPIOs

• Internal oscillator requires no external components

• 12C-bus interface logic compatible with SMBus

• Internal power-on reset

• Noise filter on SCL JSDA inputs

• Active LOW reset input (RESET)

• 2 open-drain outputs directly drive LEDs to 25 mA

• Edge rate control on outputs.  

• No glitch on power-up

• Supports hot insertion

• Low standby current

• Operating power supply voltage range of2.3V to 5.5V

• 0 Hz to 400 kHz clock frequency

• ESD protection exceeds 2000 V HBM per JESD22-A114, 150 V MM perJESD22-A115 and 1000 V CDM per JESD22-C101

• Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

• Packages offered: SO8, TSSOP8 (MSOP8)

Typical Application