LM8323 datasheet(6/46 Pages) TI2

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SF Keys

LM8323

Keypad

I/O Controller

KP-Y1

KP-Y2

KP-Y3

KP-Y4

KP-Y5

KP-Y6

KP-Y7

KP-Y8

KP-X0

KP-X1

KP-X2

KP-X3

KP-X4

KP-X5

KP-X6

KP-X7

Host

Processor

SDA

SCL

VCC

KP-Y0

CONFIG_1

CONFIG_2

GPIO_14

GPIO_15

PWM_0

PWM_1

RESET

VCC

GND

XTAL_IN

XTAL_OUT

IRQ

ROT_IN_1

ROT_IN_2

ROT_IN_3

LM8323

SNLS273A – JULY 2010 – REVISED MARCH 2013

www.ti.com

APPLICATION EXAMPLE

Figure 2. Typical Application

FEATURES

The application example shown in Figure 2 supports the following features:

•

8 x 9 standard keys.

•

8 special function keys (SF keys) with wake-up capability by forcing a WAKE_INx pin to ground. Pressing a

SF key overrides any other key in the same row.

•

ACCESS.bus (I2C-compatible) interface for communication with the host.

•

Hardware IRQ interrupt to host to signal keypad, rotary encoder, error, and status events. By default, this is

an open-drain output, so an external pullup resistor may be required to avoid false assertion. The host can

program this output for push-pull mode, in which case the pullup might not be required, if the host can ignore

a false assertion before the LM8323 has been programmed.

•

Two LEDs driven by PWM outputs with programmable ramp-up and ramp-down. PWM_2 (shared with

GPIO_15 and CONFIG_2) could be used as an additional PWM driver port to control a third external LED.

•

Rotary encoder interface shares pins with KP-Y9, KP-Y10, and KP-Y11. For larger keyboard configurations

(such as QWERTY layouts), the rotary encoder interface is not available.

•

ACCESS.bus address is selected by the CONFIG_1 and CONFIG_2 inputs. These pins may also be used as

GPIO pins after reset initialization has occurred. If extra GPIO pins are not needed, CONFIG_1 and

CONFIG_2 may be tied directly to VCC and GND.

•

Crystal pins XTAL_IN and XTAL_OUT may be used to connect to an external 32.768 kHz crystal or receive

an external 32.768 kHz clock input for running the PWM peripheral. By default, the PWM is clocked by an on-

chip clock source.

CLOCKS

•

System Clock (mclk) — The system clock is in the range of about 21 MHz (±7%) typical. This clock is used

to drive the I2C-compatible serial ACCESS bus and is the input clock for other function blocks.

•

Processing and Command Execution Clock (tC) — The internal processing is based on a 2MHz clock. This

clock is derived from the System Clock.

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