UM1551 datasheet(7/17 Pages) STMICROELECTRONICS

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UM1551

Description

If the VDD is powered from VEXT (no matter if directly or using onboard LDO), there should

be an external pull-up resistor to VDD connected to the CHARGING/ATTACH output to

ensure its proper function in the case of VIN turned off.

Auxiliary and indication circuits

Test points

All the important signals are available on test points.

The DP_IN, DM_IN, DP_OUT and DM_OUT signals are isolated from the high speed USB

bus by 10 k

 resistors. The purpose of these test points is to verify DC values and various

detection/negotiation processes only, not to evaluate the AC performance of the STCC50x1

device.

The AC performance of the USB data switch (eye-diagram tests for instance) can, of

course, be evaluated using the demonstration board USB connectors J2 and J3 when the

board is configured to SDP mode (CTLx = 110, EN = 1) and nothing connected to TP14 -

TP17.

The sensing test points TP18 and TP19 allow measurements of RDS (on) using a Kelvin

connection.

LEDs

The board is equipped with indication LEDs to allow easy visual verification of these vital

signals: VIN, FAULT, CHARGING/ATTACH, VOUT.

The VOUT LED is isolated from the VOUT line by Q1 to prevent false attach detection caused

by LED current.

Decoupling components

The capacitors C1, C2, C3 and C4 are recommended decoupling components for the

STCC50x1 device. They are recommended values, types and placements and can be used

as a guide for application design.

UM1551 Datasheet(PDF) 7 Page - STMicroelectronics