LM5145 datasheet(19/55 Pages) TI

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UV2

UV1

IN(on)

(2)

VIN

1.2 V

Enable

comparator

RUV1

RUV2

LM5146

EN/UVLO

Remote

shutdown

10 A

vcc

Figure 8-3. Programmable Input Voltage UVLO Turn-on and Turn-off

The LM5146 enters a low IQ shutdown mode when EN/UVLO is pulled below approximately 0.4 V. The internal

LDO regulator powers off and the internal bias supply rail collapses, shutting down the bias currents of the

LM5146. The LM5146 operates in standby mode when the EN/UVLO voltage is between the hard shutdown and

precision enable (standby) thresholds.

8.3.5 Power Good Monitor (PGOOD)

The LM5146 provides a PGOOD flag pin to indicate when the output voltage is within a regulation window. Use

the PGOOD signal as shown in Figure 8-4 for start-up sequencing of downstream converters, fault protection,

and output monitoring. PGOOD is an open-drain output that requires a pullup resistor to a DC supply not greater

than 13 V. The typical range of pullup resistance is 10 kΩ to 100 kΩ. If necessary, use a resistor divider to

decrease the voltage from a higher voltage pullup rail.

LM5146

1 EN/UVLO

RUV1

499 k

VOUT(MASTER) = 5 V

RFB1

RFB2

20 k

3.83 k

0.8 V

LM5146

RPG

20 k

RFB3

RFB4

20 k

6.34 k

0.8 V

VOUT(SLAVE) = 3.3 V

VIN(on) = 15 V

VIN(off) = 10 V

Regulator #1

Start-up based on

input voltage UVLO

Regulator #2

Sequential start-up

based on PGOOD

PGOOD 10

RUV2

43.2 k

EN/UVLO

Figure 8-4. Master-Slave Sequencing Implementation Using PGOOD and EN/UVLO

When the FB voltage exceeds 94% of the internal reference VREF, the internal PGOOD switch turns off and

PGOOD can be pulled high by the external pullup. If the FB voltage falls below 92% of VREF, the internal

PGOOD switch turns on, and PGOOD is pulled low to indicate that the output voltage is out of regulation.

Similarly, when the FB voltage exceeds 108% of VREF, the internal PGOOD switch turns on, pulling PGOOD low.

If the FB voltage subsequently falls below 105% of VREF, the PGOOD switch is turned off and PGOOD is pulled

high. PGOOD has a built-in deglitch delay of 25 µs.

www.ti.com

LM5146

SNVSBV0A – JUNE 2021 – REVISED JUNE 2021

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