WM8351 datasheet(147/330 Pages) WOLFSON

147 / 330 page

Production Data

WM8351

PD, April 2012, Rev 4.5

147

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R172 (ACh)

Current Sink

Driver A

5:0

CS1_ISEL

00 0000

ISINKA current = 4.05µA × 2

CS1_ISEL/4

where CS1_ISEL is an unsigned binary

number

Minimum: 00 0000 = 4.05µA,

Maximum: 11 1111 = 220mA

(from circuit simulation)

CS1_ISEL = 13.3 × log (desired current /

4.05µA)

Table 97 Controlling the Sink Current for ISINKA

Note that currents above 40mA are not supported continuously; these settings are intended for flash

mode only.

16.2.3

FLASH MODE

The current sink can either sink current continuously (LED mode) or in short bursts (flash mode). The

operating mode is selected by the CS1_FLASH_MODE bit, as described in Table 98.

In LED mode, the current sink is controlled by setting CS1_DRIVE. For as long as this bit is asserted,

the LED is enabled continuously.

In Flash mode, the current sink may be set to automatically flash every 4 seconds by setting

CS1_FLASH_RATE = 1, or may be triggered normally by setting CS1_FLASH_RATE = 0.

When normal triggering is selected in Flash mode, the trigger control can be either a GPIO Flash

input (see Section 20) or a register control. Setting CS1_TRIGSRC = 1 selects GPIO as the trigger.

The flash will be edge triggered by the selected GPIO input. Setting CS1_TRIGSRC = 0 selects the

this bit will be reset at the end of the flash.

In all flash modes, the duration of each flash is set by CS1_FLASH_DUR. The status of each current

sink may be read from the CS1_DRIVE bit.

In all modes, the current sink must also be enabled via the applicable CS1_ENA bit (see Table 96).

Note that some photo-flash applications may require a reservoir capacitor to store sufficient charge

for the flash.

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