Gcap Ii Ic U501 - Motorola ASTRO XTS 5000 Detailed Service Manual

Detailed Theory of Operation

4.3.3.1 GCAP II IC U501

The GCAP II IC is a mixed-signal (analog and digital) IC that provides control, audio, and voltage
regulation functionality. It comes in a 100-pin, ball-grid array (BGA) package with 0.8 mm pitch solder
balls. The GCAP II IC is supplied with switched battery voltage GCAP_B+ (R581).
4.3.3.1.1 Voltage Regulation
The GCAP II IC contains several voltage regulators that are used in the design of the VOCON board:
VSW1, VSW2, and V2. The VSW1 regulator is a programmable switching regulator that uses the
switched battery voltage as its input on pin PSRC1. The output voltage of VSW1 (R502) is
programmable by the Patriot IC U401 through the SPI bus. The initial output of VSW1 is 3.2 volts,
which is then programmed to 3.8 volts. The VSW1 voltage is supplied to the RF Interface connector
P201 pin 15 and to the input pins of the VSW2 and V2 regulators.
The VSW2 regulator is a SPI programmable switching regulator that uses VSW1 as its input on pin
PSRC2. The initial output of VSW2 (R501) is 2.2 volts, which is then programmed to 1.875 volts
(referred to as 1.8 volts throughout this document). The VSW2 voltage is supplied to the Patriot IC
(core voltage and the EIM voltage), the SRAM U403, the Flash memory U402, and the display
module connector J301.
The V2 regulator is a SPI programmable linear regulator that uses VSW1 as its input on pin VIN2.
The initial output of V2 (R560) is 2.775 volts, which is then programmed to 3 volts. The V2 voltage is
supplied to the Patriot IC (I/O ring - SPI, BBP, SAP, UART, GPIO, etc.), the Flipper IC U301, the
EEPOT U509, and the many discrete components that interface with the Patriot IC and the Flipper
IC.
4.3.3.1.2 MCU Interface
The GCAP II IC has a four-wire, SPI connection to the Patriot IC (SPI B). The SPI B clock is
connected to the SPI_CLK pin (test point SCKB). The SPI B MOSI line is connected to the SPI_DW
pin (test point MOSIB). The SPI B MISO line is connected to the SPI_DR pin (test point MISOB). The
GCAP SPI B chip-select signal is connected to the CE pin (R539). Through this interface, the Patriot
IC can program the voltage regulators, the CODEC, the transmit and receive audio filters and
amplifiers, as well as read information from the ADC and the real-time clock.
The GCAP II IC has an 8-bit ADC with general-purpose six channels and four voltage-monitoring
channels. The six general-purpose analog-to-digital (A/D) channels are assigned to monitor volume
(AD5); the three-position toggle switch from the universal connector J101 (AD1); the emergency,
monitor, and side buttons (AD0); the battery status line (AD2); the board type indicator (AD3); and
the board identification voltage (AD4). Battery voltage is also monitored by the ADC. The Patriot IC
activates and reads the A/D values through the SPI bus.
The real-time clock (RTC) module of the GCAP II IC consists of several counters to determine
elapsed time. The Patriot IC reads the RTC registers through the SPI bus. The RTC is supplied with
voltage from a backup lithium rechargeable battery (LI_CELL) and a 32.768 kHz clock signal from
the Flipper IC to the GCAP II IC XTAL1 pin.
68P81094C31-O
: VOCON Board 4-17
April 15, 2002