Motorola SSETM 5000 Universal Connector and Option Selects, Universal Side Connector

Theory of Operation: VOCON Board 2-29

2.5.2.3.2 ESD Protection Circuitry

NOTE: See Figure 12-13. NCN6186_ VOCON Universal Connector Circuit on page 12-19.

Several components on the VOCON board protect the circuitry from ESD. The side connector signal lines have ESD protection components on them since they are exposed. These protection components include:

•5.6-V zeners VR205, VR206, VR220, and VR221 on the SB9600 lines, RS232 lines, microphone lines, and option-select lines

•12-V zeners VR201, VR203, and VR209 on the internal and external speaker and microphone audio lines

•13-V zener VR204 on the OPTB+ line

•Low-capacitance ESD suppressors C205, C206, C209 D203, VR220,VR221, and VR205 on audio lines, USB datalines, and option-select lines

There were also several protection diodes on lines connected to the digital-support IC. These include C224, C225, C226, C227, VR205, and VR206. ESD protection for the battery status line is provided by a 5.6-V zener VR501.

2.5.2.3.3 Universal Connector Interface Circuitry

Some important components on the universal connector interface are two op-amps. The first op- amp, U201, is used as a unity-gain buffer for the option-select line. Similarly, the other op-amp, U202, is used as a comparator for the buffered option-select line. The comparator threshold is determined by the voltage-divider network of R240 and R243.

Universal Connector and Option Selects

The universal connector is located on the back of the radio. It is the external port or interface to the outside and is used for programming and interfacing to external accessories. The universal connector connects to the VOCON board at connector J102 via a flex circuit that is routed inside the external housing. Figure 2-9shows the pinout for the universal side connector, and Table 2-10shows the pin assignments. Connections to J102 on the VOCON board are shown in Figure 2-10.

1	2	3
EXT_SPKR_NEG	EXT_SPKR	LHDATA
4	5	6
EXT_MIC	CTSOUT	LHBUSY
7	8	9
OPT_SEL	OPT_B+/VPP	RTSIN/KEYFAIL
10	11	12
1-WIRE	RS232_DOUT/USB_D+	RS232_DIN/USB_D-

Figure 2-9. Universal Side Connector

6881094C12-A November 11, 2004