5

ACE9020

Power Control Circuits

The inputs PD1 and PD2 are used to select the operating

modes as shown below:

PD1

PD2

Mode

0

0

Sleep

All circuits off

1

0

Standby

Prescaler On

1

1

Transmit Set Up

Prescaler, VHF

oscillator on. Upconverter off

0

1

Duplex

All circuits on

The power down inputs (PD1, PD2) are compatible with

ACE9030 digital outputs (DO5, 6, 7). These modes allow

circuit operation and power consumption to be optimised. The

ACE9020 can be put in sleep mode (0, 0) when the power

consumption is minimal. The standby mode (1, 0) is used

when the phone is in standby (receive only). The prescaler is

operational to maintain the main UHF PLL; all circuitry

associated with transmit functions is turned off.

There is an intermediate transmit set up state (1, 1). This

allows the VHF oscillator and phase locked loop to stabilise

before enabling the upconverter, preventing spurious

transmissions. The time required for this state will be

determined primarily by the VHF PLL settling time. The power

down inputs can then be set to (0, 1) the full duplex condition.

The intermediate state should also be used during a ‘handoff’

during conversation on an analogue cellular phone, the VHF

PLL continuing to operate while the main UHF PLL changes

channel, the transmit output being disabled. It is also

recommended that the intermediate state is used when going

from duplex (0, 1) to standby (1, 0) modes.

Operating Notes

Good RF layout techniques should be used for this device

to obtain optimum performance and also minimise crosstalk

between circuit blocks. RF supply decoupling should be

provided adjacent to Vcc pins; a value of 27pF is

recommended.

Two external bias resistors are required. A 22k

Ω resistor

is connected from BIAS REF (Pin 4) to ground. This sets an

accurate reference current for the chip. An 18k resistor is

connected from RSET TXPA (Pin 8) to ground which controls

the output level of the VHF oscillator and hence the TXPA

output level.

Fig. 4 Application Diagram