LM3537 datasheet(22/33 Pages) TI2

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LM3537

SNVS634B – JUNE 2011 – REVISED MAY 2013

www.ti.com

Table 5. Control Register Map (continued)

Hex

Read/W

Default Value

Bit(s)

Bit Mnemonic and Description

Addr.

rite

After Reset

OPTIONS

[7:6]

R/W

00xxxxxx

Charge pump gain transition filter. The value stored in this register

determines the filter time used to make a gain transition in the event

of an input line VIN_A step. Filter Times (typ.) = ‘00’ = 3-6ms, ‘01’ =

0.8-1.5ms, ‘10’ = 20µs, '11' = 1µs,

[5:3]

R/W

xx000xxx

Diode current ramp down step time: ‘000’ = 6µs, ‘001’ = 0.77ms,

‘010’ = 1.5ms, ‘011’ = 3ms, ‘100’ = 6ms, ‘101’ = 12ms, ‘110’ = 25ms,

‘111’ = 50ms

[2:0]

R/W

xxxxx000

Diode current ramp up step time : ‘000’ = 6µs, ‘001’ = 0.77ms, ‘010’

= 1.5ms, ‘011’ = 3ms, ‘100’ = 6ms, ‘101’ = 12ms, ‘110’ = 25ms, ‘111’

= 50ms

ALS ZONE

[7:6]

00xxxxxx

rev

READBACK

Stores the silicon revision value. LM3537 = '00'

[5]

xx0xxxxx

als_gain

Gain_status indicator: '1' = high gain, '0' = low gain.

[4]

xxx0xxxx

timerflag

At the end of every countdown, the timer sets the timerflag ='1'. The

flag bit is cleared once the 0x40 register has been read.

[3]

xxxx0xxx

zoneflag

ALS transition flag. '1' = Transition has occurred. '0' = No transition.

The flag bit is cleared once the 0x40 register has been read.

[2:0]

xxxxx000

zone

ALS Zone information: '000’ = Zone0, ‘001’ = Zone1, ‘010’ = Zone2,

‘011’ = Zone3, ‘100’ = Zone4. Other combinations not used.

ALS CONTROL

[7:5]

R/W

000xxxxx

ave

Sets averaging time for the ALS sampling. Need two to three

averaging periods to make transition decision.‘000’ = 25ms, ‘001’ =

50ms, ‘010’ = 100ms, ‘011’ = 200ms, ‘100’ = 400ms, ‘101’ = 800ms,

‘110’ = 1.6s, ‘111’ = 3.2s.

[4:3]

R/W

xxx00xxx

timer

Pre-defined countdown timer function.

'00' = countdown timer is disabled

'01' = 10s countdown timer is enabled (stick to the highest zone for

10s)

'10' = Always stick to the highest zone the ALS reached

'11' = Always stick to the highest zone the ALS reached.

At the end of every countdown, the timer sets the countdown

timerflag (reg 40H), and after that, a Zone transition to a lower Zone

re-loads the timer and starts the next timer period.

[2]

R/W

xxxxx0xx

als_en

Enables ALS monitoring. Writing a '1' enables the ALS monitoring

circuitry and a '0' disables it. This feature can be enabled without

having the current sinks or charge pump active. The ALS value is

updated in register 0x40 ALS ZONE READBACK.

[1]

R/W

xxxxxx0x

als_en_a

Enable ALS on Group A. Writing a '1' enables ALS control of diode

current and a '0' (default) forces the Group A current to the value

stored in the Group A brightness register. The als_en bit must be set

to a '1' for the ALS block to control the Group A brightness.

[0]

R/W

xxxxxxx0

als_en_b

Enable ALS on Group B. Writing a '1' enables ALS control of diode

current and a '0' (default) forces the Group B current to the value

stored in the Group B brightness register. The als_en bit must be set

to a '1' for the ALS block to control the Group B brightness. The ALS

function for Group B is different than Group A in that the ALS will

only enable and disable the Group B diodes depending on the ALS

zone chosen by the user. Group A utilizes the 5 different zone

brightness registers (Addresses 0x70 to 0x74).

ALS RESISTOR

[4:0]

R/W

xxx00010

r_als

Sets the internal ALS resistor value. See Table 1 for details.

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