MP1497 – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

MP1497 Rev. 1.05

www.MonolithicPower.com

10

12/26/2012

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2012 MPS. All Rights Reserved.

under-voltage (UV) threshold—typically 50%

below the reference. Once UVP triggers, the

MP1497 enters hiccup mode to periodically

restart the part. This protection mode is

especially useful when the output is dead-

shorted to ground. The average short-circuit

current falls to alleviate thermal issues and to

protect the regulator. The MP1497 exits hiccup

mode once the over-current condition is

removed.

Thermal Shutdown

Thermal shutdown prevents the chip from

operating at exceedingly high temperatures.

When the silicon die temperature exceeds

150°C, it shuts down the whole chip. When the

temperature drops below its lower threshold

(typically 130°C) the chip is enabled again.

Floating Driver and Bootstrap Charging

An external bootstrap capacitor powers the

floating power MOSFET driver. This floating

driver has its own UVLO protection with a rising

threshold of 2.2V and a hysteresis of 150mV.

The bootstrap capacitor voltage is regulated

regulate M1 to maintain a 5V BST voltage

across C4. A 10Ω resistor placed between SW

and BST cap. is strongly recommended to

reduce SW spike voltage.

Figure 3: Internal Bootstrap Charging Circuit,

Startup and Shutdown

thresholds, the chip starts. The reference block

starts first, generating stable reference voltage

and currents, and then the internal regulator is

enabled. The regulator provides stable supply

for the remaining circuitries.

Three events can shut down the chip: EN low,

shutdown procedure, the signaling path is first

blocked to avoid any fault triggering. The

COMP voltage and the internal supply rail are

then pulled down. The floating driver is not

subject to this shutdown command.