Motorola SSETM 5000 - Manual (Page 56)

November 11, 2004 6881094C12-A
2-34 Theory of Operation: VOCON Board
Figure 2-12. VOCON Receive Audio Path
2.5.6 Radio Power-Up/Power-Down Sequence
The radio power-up sequence begins when the user closes the radio On/Off switch on the control
top, placing 7.5 Vdc on the B+SENSE line. This voltage enables the pass element Q501 and Q502,
enabling SW_B+ and GCAP_B+.
When the GCAP II IC U501 detects a low-to-high voltage transition on GCAP_B+, it turns on and
enables voltage supplies VSW1, VSW2, V2 and Vref. As soon as these voltages come up, the
1.55 V regulator ramps up (only on the VOCON board), and the digital-support IC U301 drives the
WDI line high to enable VCC5 from regulator U505 and to maintain the GCAP II IC in the ON state. If
WDI remains low, the GCAP II IC turns off 50 ms after turning on.
The radio power-down sequence begins by opening the radio On/Off switch, which removes the
B+SENSE signal from the VOCON board. This does not immediately remove power because the
GCAP II IC has control of Q502 through Vref, and U301 through WDI maintains the GCAP II IC in an
active state. Both the MCU and digital-support IC monitor B+SENSE. After B+SENSE is removed,
the digital-support IC waits 125 ms. before releasing WDI to allow for software cleanup; however, the
software has the ability to prolong this time if it was necessary to complete its operations. When WDI
is released, the GCAP II IC shuts down its supplies and the rest of the radio through Q501.
GCAP II IC U501
LP FILTER
cutoff = 3.5KHZ
HP FILTER
cutoff = 200HZ
GCAP CODEC
13-bit D/A
PGA
-35 to 0dB
in 5dB steps
Default 0dB
GCAP A4
Gain = 1.5
(3.5dB)
Audio_PA_Enable
0
0
1
1
Audio_Mode_Sel
0
1
0
1
Audio PA Status
Audio Off
Mute
Audio On
Audio On
Mode (V)
1.5V <V_mode<6V
<0.5V
>7V
PA Status
Mute
Audio On
Audio Off
Select (V)
B+ (7.5V)
<0.5V
Internal Speaker
Internal Speaker
External Speaker
ABACUS III
U500
(On RF Board)
RX_SSI_FSYNC
RX_SSI_CLK
RX_SSI_DATA
Audio PA Enable
Control circuits
1/2 Q505
Audio PA Mute
Control
Q506,R564,R559
Int/Ext SPKR SEL
Control circuits
1/2 Q505, R558
Flipper
U301
CODEC_FSYNC
PATRIOT
SAP/BBP
CODEC_RX
PATRIOT
SPI B
PATRIOT
GPIO
EXT PRE-AMP
U502
Gain set by
R537 and R551
AUDIO PA U503
Gain set by R550,
R554, R549, and
R553
MODE SELECT
External
Speaker
28 Ohm
Internal
Speaker
4
GCAP_CE, SCKB
SPI_MOSIB
SPI_MISOB CODEC_DCLK
EXTOUT
TP212
TP2123
AUDIO_PA_ENABLE AUDIO_MODE_SEL EXT_SPKR_SEL
3
MAEPF-27417-A