MPQ4491M–SMART, SINGLE USB CHARGING PORT POWER CONVERTER

WITH SELECTABLE FREQUENCY FOR AUTOMOTIVE, AEC-Q100 QUALIFIED

MPQ4491M Rev. 1.01

www.MonolithicPower.com

13

6/5/2017

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

© 2017 MPS. All Rights Reserved.

USB CURRENT-LIMIT SWITCH SECTION:

Current-Limit Switch

The MPQ4491M integrates a single-channel,

USB current-limit switch that provides built-in,

soft-start circuitry that controls the rising slew

rate of the output voltage to limit inrush current

and voltage surges.

When the load current reaches the current-limit

threshold (typically 2.75A), the USB power

MOSFET switches into foldback current-limit

mode, 70% of the current limit (see Figure 4). If

the over-current limit condition lasts longer than

3ms, the chip enters hiccup mode with a 3ms

on time and an 8.5s off time.

Figure 4: Over-Current Limit

cannot exceed 70% of the current limit to avoid

triggering a foldback current limit and causing a

start-up failure.

Output Line Drop Compensation

The MPQ4491M can compensate for an output

voltage drop, such as high impedance caused

by a long trace, to maintain a fairly constant 5V

load-side voltage.

The MPQ4491M uses the internal current-

sense output voltage of the current-limit switch

to compensate for the line drop voltage. Since

the trace resistance varies for different cables,

the MPQ4491M provides selectable line drop

compensation through VDROP. The line drop

compensation amplitude increases linearly as

the load current increases, and also has an

upper limitation.

USB Output Over-Voltage Protection (OVP)

The USB switch’s output uses a dynamic over-

voltage protection (OVP) threshold to protect

the

device

at

its

cable

terminal.

The

MPQ4491M adjusts the OVP threshold based

on different USB loading currents.

The MPQ4491M uses intelligent line drop

compensation and a dynamic over-voltage

protection control scheme to ensure that the

voltage at the cable terminal meets the 4.75V-

5.25V specification.

USB Output Discharge

The USB portion involves a discharge function

that provides 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.

Auto-Detection

The MPQ4491M integrates the USB dedicated

charging port auto-detect function, which

recognizes most mainstream portable devices.

It supports the following charging schemes:

 USB battery charging specification BC1.2/

Chinese

Telecommunications

Industry

Standard YD/T 1591-2009

 Divider mode

 1.2V/1.2V mode

The auto-detect function is a state machine that

supports all of the DCP charging schemes

above.

For MPQ4491MGRE and MPQ4491MGRE-

AEC1, after power startup, it will enter default

divider mode, output voltage is 5.05V with full

line drop compensation. If it enters BC1.2 short

mode or 1.2V/1.2V mode, output voltage will

change

to

5.25V

with

half

line

drop

compensation. By doing this, the device uses

BC1.2 mode or 1.2V/1.2V mode that can

charge at its full rated current.

For MPQ4491MGR and MPQ4491MGR-AEC1,

the output voltage is always 5.05V with full line

drop compensation no matter which charging

mode it is.

Thermal Shutdown

Thermal shutdown prevents the chip from

operating at exceedingly high temperatures.

When the silicon die temperature exceeds

165°C, the entire chip shuts down. When the

temperature falls below its lower threshold,

typically 145°C, the chip is enabled again.