Motorola SSETM 5000 - Manual (Page 51)

6881094C12-A November 11, 2004
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 2-9 shows the pinout for the universal side connector, and Table 2-10
shows the pin assignments. Connections to J102 on the VOCON board are shown in Figure 2-10 .
Figure 2-9. Universal Side Connector
1 2
12 11 10
9 8 7
4 5 6
3
EXT_SPKR_NEG EXT_SPKR LHDATA
EXT_MIC CTSOUT LHBUSY
OPT_SEL OPT_B+/VPP RTSIN/KEYFAIL
1-WIRE RS232_DOUT/USB_D+ RS232_DIN/USB_D-