TSU6721 datasheet(12/45 Pages) TI2

12 / 45 page

TSU6721

GND

D+

D-

VBUS

SRC

REF

ID,MAX

(1)

TSU6721YFF

SCDS345 – JUNE 2013

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ACCESSORY ID DETECTION

If VBUS is high and the attachment is a non-compliant charger (see Table 5), the impedance on the ID pin is

then determined. If VBUS is low and an accessory is attached, then an ADC for impedance sensing is used on

the ID pin to identify which accessory is attached and/or what kind of remote control key button is pushed.

The TSU6721 features impedance detection for identification of various accessories that might be attached to the

micro-USB port. Each accessory is identified by a unique resistor value connected between the ID pin and

Ground. During impedance detection a current source is applied to the ID pin. The current source is then applied

to the ID pin while an internal voltage reference is incremented till it matches the ID pin voltage. This produces a

5-bit ADC value that corresponds to the ID resistance found. Once an ID resistance is identified, a current source

is continuously applied to determine when the resistance is detached.

(1)

Maximum ID_Cap capacitance as noted in RECOMMENDED OPERATING CONDITIONS

Figure 1. Impedance Detection Circuitry

Impedance Buckets for Each Accessory and Remote Control Key Button

In order to implement ID detection, each accessory and remote control key button of audio accessory should

contain below ID impedance resistor value which is 1% tolerance accuracy.

Switch Matrix

MCPC accessory table is selected only when MCPC mode is enabled in Control Reg02h. VBUS to OUT Load

Switch is enabled anytime VBUS is applied to the USB connector.

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TSU6721 Datasheet(PDF) 12 Page - Texas Instruments