LM3530 datasheet(25/50 Pages) TI1

25 / 50 page

VALS1

437.5 mV

(500 LUX)

Brightness

Zone

LM3530 turns on

and averaging

begins

LED

Current

0 mV

Zone 0

Zone 2

Zone 4

7.38 mA

Zone 2

ALS

Average

979 mV (900 LUX)

1.3 mA

LM3530

www.ti.com

SNVS606L – JUNE 2009 – REVISED DECEMBER 2014

Figure 37. ALS Averaging Example

8.3.16 Interrupt Output

INT is an open-drain output which pulls low when the Ambient Light Sensing circuit has transitioned to a new

ambient brightness zone. When a read-back of the ALS Information Register is done INT is reset to the open

drain state.

8.3.17 Overvoltage Protection

Overvoltage protection is set at 40 V (minimum) for the LM3530-40 and 23.6 V minimum for the LM3530-25. The

40-V version allows typically up to 11 series white LEDs (assuming 3.5 V per LED + 400 mV headroom voltage

for the current sink = 38.9 V). When the OVP threshold is reached the LM3530 switching converter stops

switching, allowing the output voltage to discharge. Switching will resume when the output voltage falls to

typically 1 V below the OVP threshold. In the event of an LED open circuit the output will be limited to around 40

V with a small amount of voltage ripple. The 25-V version allows up to 6 series white LEDs (assuming 3.5-V per

LED + 400 mV headroom voltage for the current sink = 21.4 V). The 25-V OVP option allows for the use of lower

voltage and smaller sized (25 V) output capacitors. The 40-V device would typically require a 50-V output

capacitor.

8.3.18 Hardware Enable

The HWEN input is an active high hardware enable which must be pulled high to enable the device. Pulling this

pin low disables the I2C-compatible interface, the simple enable/disable input, the PWM input, and resets all

registers to their default state (see Table 4).

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