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AD6426

Enhanced GSM Processor

Analog Devices 

Preliminary Technical Information

GPIO6 - VBIAS

This general purpose I/O pin can be used to control the

powering up/down of a separate voltage converter, which may

be needed to provide the supply voltage for GaAs RF Power

Amplifiers. Significant turn-on time of the voltage converter

requires an early power-up signal, which is provided by

GPIO6. This control is achieved entirely through a software

driver, without hardware support. Since this function is not

needed for all radio solutions, the GPIO pin can be used for

other functions if not required.

GPIO7 - ANTENNASELECT

This general purpose I/O pin can be used to switch between

two different antennas, as required, when the mobile radio is

used in conjunction with a car-kit with external antenna. This

control is achieved entirely through a software driver, without

hardware support. Since this function is not needed for all

radio solutions, the GPIO pin can be used for other functions if

not required.

Tx Timing Control

The following 5 radio interface pins serve different functions

depending on the radio architecture:

TXPHASE

The purpose of this signal is to switch PLLs between Rx and

Tx modes. The signal is generated under control of the flags

TXPHASE Enable and TXPHASE Polarity of the RADIO

CONTROL CC Control Register 2.

Bit RADIO CONTROL CC Control Register 2

6 TXPHASE Polarity

Controls the polarity of the output TXPHASE.

When set to 1, TXPHASE is active low;

When set to 0, TXPHASE is active high.

3 TXPHASE Enable

Enables the output pin TXPHASE if set to 1.

0 Transmit Enable

Enables the output pin TXENABLE if set to 1.

In radios based on the TTP/Hitachi solution, this signal can be

used to switch the VCO´s.

In radios based on the Siemens or Philips solution, this signal

can be used for control switching PLLs, or band switching

UHF PLLs.

TXENABLE

This signal enables the RF modulator and transmit chain

including the PA, and controls the TXON-pin of the AD6425.

The signal is generated under control of flag Transmit Enable

of the RADIO CONTROL CC Control Register 2.

AD6426

TXPA

This signal is used as a power amplifier (PA) enable and/or as

a control signal for the PA control loop. This allows the PA to

be isolated from the supply outside the Tx-slot to save current.

In the PA control loop it can be used to control the dynamics

of the loop. The flag Tx Pa Polarity in the TRAFFIC MODE

CC Control Register 6, provides independent control for the

TXPA signal.

Bit TRAFFIC MODE CC Control Register 6

7 Tx Pa Polarity;

active high, when reset

TXPA is derived from the leading edge of TXENABLE signal

shown in Figure 7.

TXENABLE

TD

TW

TXPA

Figure 7. Timing of TXPA

The parameter TD is a programmable delay (0 to 1023 QBIT) to

accommodate the EVBC settling time. TD is therefore a 10 bit

value, accessed via the TXPA OFFSET 1 CC Control Register

73 and the TXPA OFFSET 2 CC Control Register 74.

Bit TXPA OFFSET 1 CC Control Register 73

1 : 0 TD (9:8)

Bit TXPA OFFSET 2 CC Control Register 74

7 : 0 TD (7:0)

The parameter TW is a programmable width (0 to 1023 QBIT)

which defines the PA enable time. TW is therefore a 10 bit

value, accessed via the TXPA WIDTH 1 CC Control Register

75 and the TXPA WIDTH 2 CC Control Register 76.

Bit TXPA WIDTH 1 CC Control Register 75

1 : 0 TW (9:8)

Bit TXPA WIDTH 2 CC Control Register 76

7 : 0 TW (7:0)

If TW is set to zero, then TXPA will be disabled.

This Information applies to a product under development. Its characteristics and specifications are subject to change without notice. Analog Devices assumes no

obligation regarding future manufacture unless otherwise agreed to in writing. No responsibility is assumed by Analog Devices for its use; nor for any

infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent

rights of Analog Devices.

Revision Preliminary 2.3 (June 9, ´98)

- 23 -

Confidential Information

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