MP2496M datasheet(12/17 Pages) MPS

12 / 17 page

MP2496M – STEP-DOWN CONVERTER WITH SINGLE USB CHARGING PORT

MP2496M Rev.1.0

www.MonolithicPower.com

10/10/2015

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

Buck Output Over-Voltage Protection (OVP)

The MP2496M buck converter has output over-

voltage protection (OVP). If the output is higher

than 6V, the high-side switch stops turning on,

and the low-side switch turns on to discharge the

output voltage until the output decreases to

5.75V. The chip then resumes normal operation.

If the output over-voltage can’t be discharged to

5.75V, the low-side switch turns off after the

inductor current reaches a negative current limit

and remains off until the next clock cycle is

triggered.

Floating Driver and Bootstrap Charging

An external bootstrap capacitor powers the

floating power MOSFET driver. This floating

driver has its own UVLO protection. The UVLO’s

rising threshold is 2.2V with a hysteresis of

150mV. The bootstrap capacitor voltage is

regulated internally by VIN through D1, M1, C4,

L1, and C2 (see Figure 3). If VBST-VSW exceeds

5V, U1 regulates M1 to maintain a 5V BST

voltage across C4.

VIN

VOUT

BST

Figure 3: Internal Bootstrap Charging Circuit

Start-Up and Shutdown

If both VIN and EN exceed their respective

thresholds, the chip is enabled. The reference

block starts first, generating stable reference

voltages and currents, and then the internal

regulator is enabled. The regulator provides a

stable supply for the remaining circuitries.

Three events can shut down the chip: EN low, VIN

low, and thermal shutdown. During the shutdown

procedure, the signaling path is blocked first 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.

Buck Output Discharge

The buck portion uses a discharge function to

provide a resistive discharge path for the external

output capacitor. The function is active when the

part is disabled (input voltage is under UVLO,

enable off) and is done in a very limited amount

of time. After VCC is discharged below 1V, the

buck output discharge resistor disconnects.

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