LM3492 datasheet(11/24 Pages) TI1

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LM3492, LM3492Q

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SNVS656C – SEPTEMBER 2010 – REVISED MAY 2013

Figure 17. Input Voltage UVLO Implemented by Precision Enable

Once the EN pin is pulled low, the LM3492 will perform the following functions: reset IOUT over- and under-

voltage indications and the corresponding COMM bit pattern, resume the switching frequency tuning to the

normal frequency, and resume channel 1 of the current regulator if it is disabled. Pulling the EN pin low for a

short period of about 200 ns can achieve the above functions with nearly no effect on the operation of the boost

converter and the current regulator.

Current Limit

The current limit ICL of the integrated MOSFET of the LM3492 provides a cycle-by-cycle current limit for

protection. It can be decreased by injecting a small signal current IILIM into the ILIM pin, and the relationship

between ICL and IILIM is

ICL = ICL(MAX) – 4290 IILIM

where

•

ICL(MAX) is the maximum current limit

(2)

Its typical value is 3.9A. As shown in Figure 18, IILIM can be provided by connecting a resistor RILIM from the VCC

pin to the ILIM pin. The typical voltage on the ILIM pin is 0.7V. To obtain the maximum current limit, connect the

ILIM pin to the ground.

Figure 18. Programmable Current Limit

Thermal Protection

Thermal protection is implemented by an internal thermal shutdown circuit, which activates at 165°C (typically) to

disable the LM3492. In this case, the LDO regulator is turned off and the CDHC pin is internally grounded.

Thermal protection helps prevent catastrophic failures from accidental device overheating. When the junction

temperature of the LM3492 falls back below 145°C (typical hysteresis = 20°C), the LM3492 resumes normal

operation.

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LM3492 Datasheet(PDF) 11 Page - Texas Instruments