Table 3-4. Pulse Switching Combination; Figure 3-19. 5V Switched Power Supply - Motorola APX 3000 Detailed Service Manual

Theory of Operation
: Controller
3.2.2.1.3 External Switcher 5
The controller board uses an external TI regulator (TPS62110, U6505) to regulate to 5.4V. The
TPS62110 is a 1.5A capable synchronous step down converter. The output is adjusted using a
voltage divider to the feedback pin. The regulator is powered from SW_B+.
the SW5 circuitry. The SW5 circuit also includes or-gate logic that facilitates implementation of
current saving PFM mode when the radio is in standby mode.
C6549
BGAP_COMP
PA_SHTDN
5V_PWM_EN
APX 3000 has Pulse Switching option.
Mode 1: Pulse Frequency Modulation (PFM). A relatively noisy but highly efficient pulsing mode for
Switched power supplies.
Mode 2: Pulse Width Modulation (PWM). Pulsing mode that is cleaner than PFM, used when risk of
RF interference is present which includes both transmit and receive radio modes.
SW_B+
VIN
C6565
EN
SYNC

Figure 3-19. 5V Switched Power Supply

Table 3-4. Pulse Switching Combination

PA_SHTDN 5V_PWM_EN
0 0
0 1
1 0
1 1
VOUT
U6505
TPS62110
SYN MODE
0 PFM
1 PWM
1 PWM
1 PWM
3-27
Figure 3-19.illustrates
V_SW_5
L6504
C6567
C6566