Motorola ASTRO MT 1500, Руководство по обслуживанию, Страница: 145 / 817

6816985H01-B August 16, 2007
900 MHz Detailed Theories of Operation: VOCON Functional Blocks 4.5-5
U102 senses the temperature of the printed circuit board (PCB) near the N-Channel MOSFET final
( Q101 ) and provides a DC level representative of this temperature to pin 30 of the PCIC. The PCIC
uses this input to cut back the output power level after a certain temperature threshold is reached.
This ensures:
1. Radio integrity while transmitting in extreme ambient conditions hotter than the radio’s
operating temperature range.
2. Acts as a safety feature to prevent any thermal runaway fault conditions.
Pin 32 of the PCIC powers the Temperature Sense IC ( U102 ) and forward biases the antenna switch
diodes ( CR101 and CR102 ) while the radio is in transmit mode. This routes the RF signal from the
transmitter to the antenna, as explained above. The antenna switch diodes are unbiased during
receive and standby modes; therefore, any RF signal present at the antenna is applied to the
receiver.
4.5.6 VOCON Functional Blocks
The three main functional blocks of the VOCON section consist of the following sections:
• the Controller and Memory Section, consisting of the following components:
- the Patriot IC (U800)
- the dual-core processor with the microcontroller unit (MCU) and a digital signal processor
(DSP)
- the SRAM IC (U804) and FLASH IC (U803) memory devices.
• the Audio and Power Section and digital support are all embedded into the MAKO IC (U701).
• the Interface Support Section, consisting of the following components:
- the ESD protection circuitry
- the side connector interface circuitry, and
- the Option board.
4.5.6.1 Controller and Memory Section
Three main ICs are in the controller and memory section of the main board schematic: the Patriot IC
(U800), the static RAM (SRAM) (U804), and the Flash memory (U803).
4.5.6.1.1 Patriot IC (U800)
The Patriot IC (U800) is a dual-core processor containing both a 32-bit microcontroller unit (MCU)
and a 16-bit digital signal processor (DSP) in one IC package. It comes in a 256 pin, ball grid array
(BGA) package with 1mm pitch solder balls. The Patriot is supplied with two voltages: 1.875 volts
(E801) and 2.9 volts (E800). The 1.875-volt supply is used as the core voltage as well as the
interface to the memory devices and display. Most of the pins on the Patriot operate from the 2.9-volt
supply.
There are two main clocks that are provided to the Patriot:
1. The CKIH pin is provided by a 16.8MHz sine wave; this is the most important clock since it is
internally used to generate the clocks for both the MCU and DSP cores, as well as most of
the peripherals.
2. A 2.9-volt peak-to-peak 32.768kHz square wave is supplied to the MCU and DSP cores. It is
generated by an external 32.768kHz crystal (Y701), and a clock buffer circuit that includes
U712, U713, U714, C742, C743, C791, C792, R745, R747, R748, R799, R741 and R742.
This signal is supplied to the CKIL pin on the dual-core processor. While not as widely used
as the 16.8MHz clock, the 32.768kHz clock is needed by some components in the dual-core
processor, including the reset circuitry.