MP1470B – SYNCHRONOUS, STEP-DOWN CONVERTER WITH INTERNAL MOSFETS

MP1470B Rev. 1.0

www.MonolithicPower.com

12

8/25/2015

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

© 2015 MPS. All Rights Reserved.

Over-Current Protection and Hiccup Mode

The MP1470B has a cycle-by-cycle over-

current limit for when the inductor current peak

value exceeds the set current limit threshold.

When the output voltage drops to trigger a UV

event (FB falls below the under-voltage (UV)

threshold (typically 140mV)), the MP1470B

enters hiccup mode to restart the part

periodically. This protection mode is especially

useful when the output is dead-shorted to

ground. This greatly reduces the average short-

circuit current to alleviate thermal issues and

protect the regulator. The MP1470B 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, the whole chip shuts down. When the

temperature falls 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.

internally through D1, M1, R4, C4, L1, and C2

regulates M1 to maintain a 5V BST voltage

across C4.

Figure 3: Internal Bootstrap Charger Start-Up

and Shutdown Circuit

thresholds, the chip starts up. The reference

block starts first, generating a stable reference

voltage and currents, and then the internal

regulator is enabled. The regulator provides a

stable supply for the remaining circuits.

Three events can shut down the chip: EN low,

procedure starts by initially blocking the

signaling path 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.