LM5122ZPWPR datasheet(14/51 Pages) TI1

14 / 51 page

IN(SHUTDOWN)

IN(STARTUP)

HYS

[V]

UV2

UV1

IN(STARTUP)

1.2V R

1.2V

ª º

¬ ¼

HYS

UV2

10 $

ª º

¬ ¼

UVLO Standby

Enable Threshold

SHUTDOWN

UVLO

Threshold

UVLO Hysteresis

Current

UVLO

RUV2

RUV1

STANDBY

SHUTDOWN

VIN

STANDBY

LM5122, LM5122-Q1

SNVS954G – FEBRUARY 2013 – REVISED MAY 2016

www.ti.com

Product Folder Links: LM5122 LM5122-Q1

Submit Documentation Feedback

7.3 Feature Description

7.3.1 Undervoltage Lockout (UVLO)

The LM5122 features a dual level UVLO circuit. When the UVLO pin voltage is less than the 0.4-V UVLO

standby enable threshold, the LM5122 is in the shutdown mode with all functions disabled. The shutdown

comparator provides 0.1 V of hysteresis to avoid chatter during transition. If the UVLO pin voltage is greater than

0.4 V and below 1.2 V during power up, the controller is in standby mode with the VCC regulator operational and

no switching at the HO and LO outputs. This feature allows the UVLO pin to be used as a remote shutdown

function by pulling the UVLO pin down below the UVLO standby enable threshold with an external open collector

or open drain device.

Figure 16. UVLO Remote Standby and Shutdown Control

If the UVLO pin voltage is above the 1.2-V UVLO threshold and VCC voltage exceeds the VCC UV threshold, a

startup sequence begins. UVLO hysteresis is accomplished with an internal 10-

μA current source that is

switched on or off into the impedance of the UVLO setpoint divider. When the UVLO pin voltage exceeds 1.2 V,

the current source is enabled to quickly raise the voltage at the UVLO pin. When the UVLO pin voltage falls

below the 1.2-V UVLO threshold, the current source is disabled causing the voltage at the UVLO pin to quickly

fall. In addition to the UVLO hysteresis current source, a 5-

μs deglitch filter on both rising and falling edge of

UVLO toggling helps preventing chatter upon power up or down.

An external UVLO setpoint voltage divider from the supply voltage to AGND is used to set the minimum input

operating voltage of the regulator. The divider must be designed such that the voltage at the UVLO pin is greater

than 1.2 V when the input voltage is in the desired operating range. The maximum voltage rating of the UVLO

pin is 15 V. If necessary, the UVLO pin can be clamped with an external zener diode. The UVLO pin should not

be left floating. The values of RUV1 and RUV2 can be determined from Equation 1 and Equation 2.

(1)

(2)

where

•

VHYS is the desired UVLO hysteresis

•

VIN(STARTUP) is the desired startup voltage of the regulator during turn-on.

Typical shutdown voltage during turn-off can be calculated as follows:

(3)

7.3.2 High Voltage VCC Regulator

The LM5122 contains an internal high voltage regulator that provides typical 7.6 V VCC bias supply for the

controller and N-channel MOSFET drivers. The input of VCC regulator, VIN, can be connected to an input

voltage source as high as 65 V. The VCC regulator turns on when the UVLO pin voltage is greater than 0.4 V.

When the input voltage is below the VCC setpoint level, the VCC output tracks VIN with a small dropout voltage.

The output of the VCC regulator is current limited at 50 mA minimum.

LM5122ZPWPR Scheda tecnica(PDF) 14 Page - Texas Instruments

LM5122ZPWPR Scheda tecnica(HTML) 14 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

Scheda tecnica Scarica

Link URL