Motorola 38C V100 Service Manual page 23

Level 3 Service Manual
6881036B20
Tx burst
TX Background
Figure 11. Transmit Operation Battery Charging
In TX background mode the Communicator requires the same current as in standby
mode, with 50mA supporting the unit and 350mA charging the battery. During TX
background, however, the EXT B+ FET Q905 is switched off causing the charger
current to be directed through the charging FET Q900.
In TX background, MIDRATE_1 = 0 and MIDRATE_2 = 1
During transmission, the communicator requires up to 1.5A to be supplied during
each burst. During a TX pulse the full 400mA from the charger supports B+ in
addition to approximately 1.1A from the battery.
In TX burst, MIDRATE_1 = 1 and MIDRATE_2 = 1
Deep Sleep Mode
Deep sleep mode saves battery life by intermittently shutting off part of the PCB
as follows: STBY_DL is generated from Whitecap IC Pin F1, through a standby
delay circuit consisting of diode CR912 and logic gate U906 which provides a short
delay between activation of STBY_PC5 and STBY_DL. This is a hardware patch
for timing issues related to the Whitecap IC's deep sleep module (DSM). The
resulting signal is passed onto Q911 and Q912 which, in turn:
• Grounds VREF, making Magic IC inoperable.
• Grounds V2, switching off Magic IC, Front END IC and inhibits the Transmit
path through RF_V2.
Deep sleep mode shutdown is only for a fraction of a second and, during that time,
the GCAP Clock supports the logic side of the unit. The GCAP clock is generated
MOTOROLA CONFIDENTIAL - PROPRIETARY
November 20, 2000
Circuit Description
I supply = I radio B + I chrg
+
400mA = 50mA + 350mA
I Tx burst = I supply + I batt contrib
1.5A = 400mA + 1.1A
.
000723-O
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