Astro Spectra Plus Voltage Regulators; Figure 3-19. Astro Spectra Plus Vocon Dc Distribution - Motorola ASTRO Digital Spectra Service Manual

Theory of Operation: ASTRO Spectra Plus VOCON Board
3.4.9

ASTRO Spectra Plus Voltage Regulators

The ASTRO Spectra Plus VOCON board contains two voltage regulators, a 3-V regulator (U411) and
a 1.8-V regulator (U410). SW+5-V, which is routed to the ASTRO Spectra Plus VOCON board from
the command board, drives the two regulators.
Spectra Plus VOCON Board.
ON
ON
Semiconductor
Semiconductor
LP2951
LP2951
ON
ON
Semiconductor
Semiconductor
LP2951
LP2951
5V
5V
SW_5V SW_5V
(from RPCIC (from RPCIC
on command
on command
board)
board)
U410 and U411 are on Semiconductor LP2951CD adjustable regulators. The output voltage of these
regulators is determined by the resistive divider network between the regulator output and the error
amplifier feedback input. The LP2951 has error output lines which are open collector and requires a
pull up resistor (R332). The error line is high when the output voltage is high and low otherwise.
U412 is a 4.2-V detect circuit for the SW_5-V line. The output of this detector is tied to the error
outputs of the LP2951 regulators as a low voltage detect (LV_detect ) circuit. C438 provides delay on
the LV_detect line during startup. This is to allow all regulators to settle prior to Patriot U300 coming
out of reset.
68P81076C25-C
V = 1.8V
V = 1.8V
V = 3.0 V
V = 3.0 V
Audio/
Audio/
5V 5V
Modulation Modulation
OP amps
OP amps

Figure 3-19. ASTRO Spectra Plus VOCON DC Distribution

Figure 3-19 shows the DC distribution for the ASTRO
2M x 16
2M x 16
PATRIOT
PATRIOT
FLASH FLASH
Core, EIM
Core, EIM
PATRIOT
PATRIOT Clock Gen
Clock Gen
Buses Buses
buffers
buffers
SSI,SPI,UART SSI,SPI,UART
MC145483
MC145483
EEPOTs EEPOTs
CODEC
CODEC
MAX5160
MAX5160
Secure Secure
Voltage
Voltage
SSI to SPI
SSI to SPI
Conversion
Conversion
conversion
conversion
block
block
circuitry
circuitry
Voltage
Voltage
USB/RS232
USB/RS232
Conversion
Conversion
quad mux
quad mux
block
block
256 x 16
256 x 16
SRAM
SRAM
16.8 MHz
16.8 MHz
Ref Osc
Ref Osc
ADDAG ADDAG
KRSIC
KRSIC
USB
USB
July 1, 2002
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