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BGY288

Power amplifier with integrated control loop for GSM850, EGSM900, DCS1800 and PCS1900

Philips Electronics 

Philips Semiconductors

BGY288

Power amplifier with integrated control loop

6.1 Ramp-up

VSTAB voltage must be available at minimum td1 before TXON goes HIGH (power control

loop activates).

BAND selects the correct transmit channel (GSM850/EGSM900, or DCS1800/PCS1900).

BAND must be at the correct value before the rising edge of TXON.

The transition of TXON to HIGH enables the power control loop; the TXON minimum td4

period is a set-up time which allows the correct internal biasing conditions and the charge

on the integration capacitors to be at the correct starting value before PC starts to

increase. RF power must be present at the input of the selected channel (PD(LB) or PD(HB))

before PC starts to ramp-up.

The required RF output power level is reached by increasing PC in steps to the

corresponding voltage level. The sequence of PC steps can be chosen to have

approximately a quarter cosine wave ramp-up of PL(LB) or PL(HB) in order to prevent

violation of the GSM power mask, and at the same time prevent violation of the spectrum

due to transients.

To avoid violation of the lowest power level in the GSM power mask (indicated by *;

see Figure 3), the BGY288 provides sufficient isolation when TXON goes HIGH with PC

at minimum value and RF power at input of power amplifier.

In LB TX mode, the system specification for maximum output power of the handset is

−36 dBm. In HB TX mode, the system specification for maximum output power of the

handset is −48 dBm. In BGY288 transmit mode, the handset antenna switch can be used

to provide isolation between the power amplifier and the antenna by setting the antenna

switch to Rx mode. This condition is used for the transmit mode isolation parameters

given in Section 9.

6.2 Ramp-down

PC steps down from the voltage level for the current power level to off state. The

sequence of PC steps can be chosen to have approximately a quarter cosine wave

ramp-down of PL(LB) or PL(HB) in order to prevent violation of the GSM power mask, and at

the same time prevent violation of the spectrum due to transients.

The power control loop can be switched off (TXON goes LOW) as soon as PC has

reached the off state level. At the same time, BAND is allowed to change polarity and the

RF input power at the selected channel (PD(LB) or PD(HB)) can be removed. When input

power is removed, there is no additional isolation specification required to meet the GSM

system specification. In LB TX mode, the system specification for maximum output power

of the handset is −54 dBm. In HB TX mode the system specification for maximum output

power is −48 dBm.

At minimum td6 after TXON goes LOW (power control loop deactivates) and when all

charge in the power control loop capacitors is removed, the BGY288 can go into Idle

mode (VSTAB = 0 V).

9397 750 14011

Preliminary data sheet

Rev. 01 — 2 February 2005

© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

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