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AD20MSP415 Datasheet(PDF) 5 Page - Analog Devices |
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AD20MSP415 Datasheet(HTML) 5 Page - Analog Devices |
5 / 8 page AD20msp415 –5– REV. 0 POWER DISSIPATION CONSIDERATIONS In mobile applications, minimizing the power consumption of all devices is critical to achieve longer standby and talk times. In a GSM handset the baseband subsystem dominates the current consumption of the phone in standby. The design of the GSMP and VBC includes extensive features to reduce power consump- tion and give standby times of up to 100 hours. Both devices are specifically designed to operate from 2.7 V to 3.3 V, to enable three or four cell battery designs. The GSMP incorporates intelligent power management, permit- ting automatic control of power consumption in the Channel Codec part of the GSMP and the peripheral circuitry. Data processing modules are switched on only when they process data, otherwise they are powered down. Additional control signals are provided that enable the Layer 1 software to control the external subsystems, such as the VBC, the radio and memory components, so that their power is intelligently switched by the GSMP. In the VBC, the power-down functions are split separately among receive, transmit and auxiliary circuits. This provides optimal analog power performance when operating in different modes. INTERFACES The chipset has eleven external interfaces (see Figure 5) that have to be considered in the design of the complete mobile radio. • Analog Voice Interface to VBC • Radio Interface to VBC and GSMP • Digital SIM Card Interface to GSMP • Digital Interface to the Keypad • Digital Bus Interface from GSMP to Memory and Display • Digital Audio Interface (DAI) • Digital Interface to GSMP for Data Services • Digital Interface from the GSMP to the EEPROM • Digital Interface from GSMP to Accessories • Digital Test Interface • Digital Interface from GSMP to Optional EFR Coprocessor Analog Voice Interface to VBC The analog voice interface to the VBC is specified in the AD6421 data sheet. Several design examples are given for single-ended or differential inputs or outputs. A voltage reference for biasing the microphone signal is provided on the VBC. The analog output of the VBC is capable of directly driving an earpiece with an impedance of 32 Ω. For optional use of a separate external microphone and power amplifier, a set of auxiliary input/output signals are provided on the VBC. Radio Interface to VBC and GSMP The analog interface between the VBC and the radio subsystem is specified in detail in the AD6421 data sheet. The digital inter- face between the GSMP and the radio subsystem is specified in detail in the AD6422 data sheet. Digital SIM Card Interface to GSMP The GSMP is designed to interface directly to the SIM. How- ever, interface logic may be necessary to connect the 3 V chipset to a 5 V SIM. Digital Interface to Keypad Keypad interface logic for up to 30 keys is provided on the GSMP. This interface provides keyboard scan for six rows and four columns. Additionally, an extra column can be imple- mented by using the “ghost column” method. Digital Bus Interface to Memory and Display External RAM and ROM, as well as the display controller, interface directly to the 21-bit address bus and 16-bit data bus of the GSMP. Interface to FLASH Memory The large FLASH memory can contain all programs for the embedded Control Processor of the GSMP. This includes the complete GSM protocol software as well as the User Interface Software. A total size of 8 Mbits is suggested, assuming a typical size of User Interface and a GSM Phase 2 Software. Enhanced features requiring larger memories are easily supported by the large address space of the embedded Control Processor. To support FLASH memory, the GSMP provides embedded code to download the software into the FLASH memory via its standard serial port. Interface to SRAM In addition to the FLASH memory, the Control Processor also supports static RAM to store user-defined variables, typically those used by the Protocol Stack or Application Layer. Standard SRAMs interface directly to the address and data bus of the GSMP. Interface to Display Controller This interface is achieved through the address and data buses and associated read and write strobes, as well as a specific en- able signal. One backlight pin with PWM control is provided by the GSMP to control brightness of backlight. Digital Audio Interface (DAI) As required by the GSM specifications, a digital audio interface is provided to allow certain tests of the audio section during type approval. This interface is activated in one of the test modes. A fully functional “DAI box” needed for the FTA process may be obtained from Analog Devices upon request. Digital Interface to GSMP for Data Services The chipset uses a serial interface that is connected to an exter- nal data terminal adapter as described in the AD6422 data sheet. Digital Interface from the GSMP to the EEPROM The GSMP provides separate pins to interface directly to an external serial EEPROM via a serial bus. This EEPROM is typically used for storage of calibration or user variable param- eters like: • Handset Identifier (IMEI) • Language • Keypad Lock • DTMF ON/OFF • Radio Calibration Parameters A typical size of the EEPROM is 2K × 8 bits, but this depends on the individual design of the handset. |
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