MP3336 – DUAL-CHANNEL, FLASH LED DRIVER WITH I

MP3336 Rev.1.01

www.MonolithicPower.com

16

5/16/2017

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3. Low

Battery

Voltage

Threshold

Is

Triggered

During flash pulse, if the battery voltage drops

below the threshold set by VBL_RUN, the

current reduces step by step until the battery

voltage rises up to the set low battery voltage

threshold. The actual current in the IFL_ACT

register can read back during flash and the

minimum current caused by the current

reduction in IFL_MIN can be read back after

flash.

Low Battery Voltage Protection

The device provides low battery voltage

protection in flash mode in the following ways:

1. Before flash, if VBL_SD = 1, and the input

voltage is lower than the threshold set by

VBL_RUN, the device remains disabled and

sets the fault bit FT_VBATL to 1. If VBL_SD

= 0, the device ramps to the current set by

I_TX and sets the fault bit FT_VBATL to 1.

The fault bit is cleared after it is read back

or when the input power resets.

2. During flash start-up, if the input voltage is

lower than the threshold set by VBL_RUN,

the current stops ramping. The fault bit

FT_VBATL is set. During flash pulse, if the

input voltage is lower than the threshold set

by VBL_RUN, the current ramps down step

by step. The fault bit is set until it is read

back or when the input power resets.

After flash, the minimum current caused by

the current reduction can be read back

through the IFL_MIN register. The IFL_MIN

value holds until the next flash occurs or

until the power resets. The actual current

can be read back through IFL_ACT during

flash. This function is useful for determining

how much flash current can be drawn from

the battery (see Figure 15).

Figure 15: Pre-Flash under Low Battery

NTC Detection

If the register NTC_WD is set to enable NTC

detection, the NTC sources a constant 35µA

current. If the voltage across the NTC resistor

drops below the threshold set by NTC_WD, the

internal fault bit FT_LEDHOT is set to 1 and the

modes are reset to standby mode if LEDT_SD

= 1. If LEDT_SD = 0, the mode setting is not

reset after the fault bit is set. The fault bit

remains until it is read back or the power resets.

It is recommended to float NTC if this function is

not being used.

Figure 16: NTC Detection

VOUT-GND Short Protection

If VOUT < 1V, the device stops switching and

disconnects the synchronous PMOS to prevent

a large current from being drawn from the

battery. Set the FT_VOSC bit to 1 and reset the

mode setting. The fault bit remains until it is

read back or the power resets.

LED1/2-GND Short Protection

If LED1 < 1V and ILED1 > 5mA, or LED2 <

1Vand ILED2 > 5mA, the IC marks off the

current source and sets the fault bit FT_LEDSC

but continues switching. If both current sources

are marked off, the device stops switching and

the mode setting is reset. The fault bit

FT_LEDSC is 1 until it is read back or the

power resets. If LED_EN1 is set to 0, the

feedback of the current source 1 is not involved