AS3685C

Datasheet

www.austriamicrosystems.com/AS3685

(ptr)

1.1

12 - 21

Table 7 – Current and Mode Setting for the AS3685

Register

Purpose

Comments

Data3<3>

Avoid 1:2 Mode

0 … Charge Pump can use 1:2 Mode

1 … Charge Pump does not use 1:2 Mode; ignored if

Data3<2:0> is set to 111 (forced 1:2 mode)

Data3<7:4>

Flash Timeout Timer

0000 … Disable Timeout timer for Flash Mode

0001 … 100ms Timeout timer for Flash Mode

0010 … 200ms Timeout timer for Flash Mode

…

1111 … 1500ms Timeout timer for Flash Mode

7.2.1 AS3685 TXMask Function

If the battery has to supply two high currents at the same time (e.g. the AS3685 flash and a RF-power amplifier) it

is possible, that the total current causes a high voltage drop on the battery resulting in a shutdown of the

complete system. In order to avoid this shutdown, the AS3685 (AS3685A or AS3685B) can reduce its current

with the signal ‘TXMask’ using the following circuit:

Figure 15 – TXMask function of the AS3685

The TXMask signal is connected to e.g. the (RF-) power amplifier enable pin (active high if the PA is enabled).

This reduces the flash current if the power amplifier is enabled and avoids the unexpected shutdown of the

system.

Note

TXMask function (see also section ‘Flash Timeout’).

V(TXMask) is the actual voltage for the high level (‘1’) for the signal TXMask

I

ISET , TXMask 0

V

ISET

R

ISET

V

ISET

R

TXMASK

1.3 V

R

ISET

1.3 V

R

TXMASK

I

ISET , TXMask 1

V

ISET

R

ISET

V

ISET

V TXMask

R

TXMASK

1.3 V

R

ISET

1.3 V V TXMask

R

TXMASK

I

LEDMAX

I

7650 I

ISET