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TDMA M3090/M3097:
EXT_B+
EXT_B+
Driver_B+
V_Buck
Description
The overvoltage circuit consist of a voltage detector (U1100) and a power switch(Q1100). A resistor divider network at the input of U1100 is used to set the EXT_B+
detect voltage to 9.2V nominal. U1100 outputs low when ever the input voltage is below the detector threshold. During normal operating voltages from EXT_B+ the gate
voltage of Q1100 is zero, which turns Q1100 on. When Q1100 is on, SW_EXT _B+ is connected to EXT_B+. Wh en EXT_B+ voltage is above 9.875V nominally, U1100
output becomes open drain. This causes the gate of Q1100 to be pulled up to the EXT_B+, which turns Q1100 off and thus disconnects the voltage to SW_EXT_B+.
Q1102-A and Q1102-B act as inverters. Therefore, a low state at the output of U1100 will result w ith a low state at the gate of Q1100 a nd vise versa.
The EXT_EN line disables the charging circuit when the phone is transmitting (as when making a call) and connected to a wall charger. It does this by cutting off the
SW_EXT_B+ line. This doe s not occur if the charg er is a CLA.
U1590 is a PA Pre-Driver Voltage Regulator that provides 3V to both 800MHz and 1900MHz RF pre-drivers.
B+ Disconnect / Driver B+
U1100
Q1102-A
U1590
Q1102-B
Q1100
EXT_EN
SW_EXT_B+
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