+

UVLO

VIN

2

3

LM5017

LM5017

SNVS783D – JANUARY 2012 – REVISED MAY 2013

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N-Channel Buck Switch and Driver

The LM5017 integrates an N-Channel Buck switch and associated floating high voltage gate driver. The gate

driver circuit works in conjunction with an external bootstrap capacitor and an internal high voltage diode. A

0.01uF ceramic capacitor connected between the BST pin and the SW pin provides the voltage to the driver

during the on-time. During each off-time, the SW pin is at approximately 0V, and the bootstrap capacitor charges

recharge the bootstrap capacitor.

Synchronous Rectifier

The LM5017 provides an internal synchronous N-Channel MOSFET rectifier. This MOSFET provides a path for

the inductor current to flow when the high-side MOSFET is turned off.

The synchronous rectifier has no diode emulation mode, and is designed to keep the regulator in continuous

conduction mode even during light loads which would otherwise result in discontinuous operation.

Undervoltage Detector

The LM5017 contains a dual level undervoltage lockout (UVLO) circuit. When the UVLO pin voltage is below

0.66V, the controller is in a low current shutdown mode. When the UVLO pin voltage is greater than 0.66V but

can be used to set the minimum operating voltage of the regulator.

UVLO hysteresis is accomplished with an internal 20

μA current source that is switched on or off into the

impedance of the set-point divider. When the UVLO threshold is exceeded, the current source is activated to

quickly raise the voltage at the UVLO pin. The hysteresis is equal to the value of this current times the resistance

UVLO

Mode

Description

<0.66V

Shutdown

Switcher disabled.

0.66V – 1.225V

Standby

Switcher disabled.

>1.225V

Standby

Switcher disabled.

Operating

Switcher enabled.

satisfied.

Figure 14. UVLO Resistor Setting

10

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