MPQ4485

– STEP-DOWN CONVERTER WITH DUAL USB CHARGING PORTS

MPQ4485 Rev.1.0

www.MonolithicPower.com

16

9/18/2017

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

© 2017 MPS. All Rights Reserved.

The auto-detect function is a state machine that

supports all of the DCP charging schemes

above. Connect DP and DM with a 150

Ω

resistor for DCP mode.

CDP Mode

USB2 supports dynamically selectable DCP or

CDP mode. Float MODE to set USB2 to DCP

mode. Pull MODE low to set USB2 to CDP

mode.

To

achieve

better

data

transmission

performance,

use

USB2

CDP

mode

for

handshaking and bypass DP to DP_OUT only.

DM to DM_OUT switches internally (see Figure

8).

DM2

DP2

Type-

A

DM2_OUT

DP2_OUT

To HOST

Controller

MPQ4485

R3, 1kΩ

L3,Bead,

1kΩ@100MHz

Figure 8: Data Transmission Enhanced Set-Up

Type-C Plug Orientation Indication (POL)

POL is an open-drain output that indicates the

Type-C plug's orientation. When POL is low,

CC1 is used as the CC pin. When POL is high,

CC2 is used as the CC pin.

USB Type-C Mode and VCONN

For USB Type-C solutions, two pins (CC1, CC2)

on the connector are used to establish and

manage the source-to-sink connection. The

general

concept

for

setting

up

a

valid

connection between a source and sink is based

on being able to detect terminations residing in

the product being attached. To aid in defining

the functional behavior of CC, a pull-up (Rp)

and pull-

down (Rd 5.1kΩ) termination model is

used based on a pull-up resistor and pull-down

resistor (see Figure 9).

Figure 9: Current Source/Pull-Down CC Model

Initially, a source exposes independent Rp

terminations on its CC1 and CC2 pins, and a

sink exposes independent Rd terminations on

its CC1 and CC2 pins, the source-to-sink

combination

of

this

circuit

configuration

represents a valid connection. To detect this,

the source monitors CC1 and CC2 for a voltage

lower than its unterminated voltage. The choice

of Rp is a function of the pull-up termination

voltage and the

source’s detection circuit. This

indicates that either a sink, a powered cable, or

a sink connected via a powered cable has been

attached.

Prior to the application of VCONN, a powered

cable exposes Ra (typically

1kΩ) on its VCONN.

Ra represents the load on VCONN plus any

resistive elements to ground. In some cable

plugs, this might be pure resistance, and in

others, it may be simply the load.

The source must be able to differentiate

between the presence of Rd and Ra to know

whether there is a sink attached and where to

apply VCONN. The source is not required to

source VCONN unless Ra is detected.

Two special termination combinations on the

CC pins as seen by a source are defined for

directly attached accessory modes: Ra/Ra for

audio adapter accessory mode and Rd/Rd for

debug accessory mode (see Figure 10 and

Table 1).

Figure 10: CC Functional Block

A port that behaves as a source has the

following functional characteristics.

1. The source uses a MOSFET to enable or

the source is disabled.

2. The source supplies pull-up resistors (Rp)

on CC1 and CC2 and monitors both to

detect a sink. The presence of an Rd pull-