ADP5520 datasheet(17/40 Pages) AD

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ADP5520

Rev. 0 | Page 17 of 40

To deassert the nINT pin and clear the KR_INT flag, Register 0x22

and Register 0x23 must be cleared by reading them once, and then

a 1 must be written to the KR_INT bit in Register 0x00. Figure 39

shows the interrupt generation scheme, where KR_x_ISTAT

represents any one of the 16-key release interrupt status bits.

AND

KP_x_ISTAT

KR_INT

KP_IEN

nINT

DRIVE

READ ONCE

TO CLEAR

REG 0x00

WRITE 1

TO CLEAR

REGISTERS

0x22 AND 0x23

REG 0x01

Figure 39. Key Release Interrupt Generation

The backlight can be programmed to turn on as a consequence

of a key press, using the KP_BL_EN bit in Register 0x02. To

enable this feature, the following sequence should be observed:

Enable the row pull-ups using Register 0x1F.

Enable key scanning on rows and columns using

Enable backlight turn-on due to key press by setting

KP_BL_EN in Register 0x02.

Set device to operating mode (nSTNBY = 1) in Register 0x00.

When a key is pressed, the backlight turns on. If the off timer is

programmed, the backlight turns off, or the user can turn off

the backlight by clearing BL_EN.

If the user wants the backlight to turn on again with a subse-

quent key press, the KP_INT and KR_INT bits in Register 0x00

must be cleared.

I/O EXPANSION PINS AND ILED PIN (AUXILIARY

LED CURRENT SINKS)

The ILED pin and two of the I/O expansion pins (R3 and C3)

can be used as auxiliary LED current sinks. Each LED current

sink is programmable up to 14 mA (typical) and can be

independently turned on and off.

The ILED pin is the current sink for LED 1. Its sink current can

be set using LED1_CURRENT in Register 0x14. The LED 1

sink can be enabled with LED1_EN in Register 0x11.

The C3 pin is the current sink for LED 2. Its sink current can be

set using LED2_CURRENT in Register 0x15. The LED 2 sink

can be enabled with LED2_EN in Register 0x11.

The R3 pin is the current sink for LED 3. Its sink current can be

set using LED3_CURRENT in Register 0x16. The LED 3 sink

can be enabled with LED3_EN in Register 0x11.

The LEDx_CURRENT registers are six bits wide, allowing the

user to set the LED sink current to one of 64 different levels

between 0 mA and 14 mA. The ADP5520 can implement two

distinct algorithms, to achieve a linear and a nonlinear

relationship between input code and sink current.

By default, the ADP5520 uses a linear algorithm (LED_LAW = 0),

where the LED sink current increases linearly for a corresponding

increase of input code. LED sink current (in milliamps) is deter-

mined by the following equation:

LED Sink Current = Code × (Fullscale_Current/63)

(3)

where:

Code is the input code programmed by the user.

Fullscale_Current is the maximum sink current allowed

(typically 14 mA).

LED1_CURRENT

LED1_EN

LED1_OFFT

LED 1

DIGITAL

COUNTERS

AND

CONTROL

ILED

VBAT

LED2_CURRENT

LED2_EN

LED2_OFFT

LED 2

DIGITAL

COUNTERS

AND

CONTROL

LED3_CURRENT

LED3_EN

LED3_OFFT

LED 3

DIGITAL

COUNTERS

AND

CONTROL

LED_FI

LED_FO

LED_LAW

LED_ONT

Figure 40. LED Current Sinks

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