HD155121F Datasheet, PDF (10/57 Pages) Hitachi Semiconductor – RF Transceiver IC for GSM and PCN Dual band cellular systems

HD155121F
Operation Modes
The HD155121F has necessary control circuitry to implement the necessary states within the dual band
system. Also provided is a power saving mode which reduces the current consumption of the device by
powering down unnecessary function blocks. Three pins are assigned for power saving mode control,
POONRX1, POONRX2 and POONTX. Also one pin is assigned for switching operational band, BAND.
Table 1 shows the relationship between the pins and the required operating mode. These pins are
controlled by the system controller.
As per GSM requirements the Tx and Rx sections do not operate simultaneously. For the receiver there is a
calibration mode in which the LNA bias circuit and first mixer are switched off. During this period the
gain of the PGA can be adjusted. Also the DC offsets of the IQ demodulator are measured and
subsequently canceled.
In order to change between the Rx and Tx modes a state called “warm-up” is used to ensure that the local
signals are not unduly affected. This method of switching between Tx and Rx ensures that lock is achieved
first time.
Power saving is implemented through use of the idle mode. All function blocks of the HD155121F are
switched off until such time as the system controller commands the device to power up again.
Table 1 Operating Modes with Power Saving
Mode
Band
POONRX1 (44)
POONRX2 (45)
POONTX (46)
BAND (35)
Rx block LNA bias (GSM)
LNA bias (PCN)
1st Mixer (GSM)
1st Mixer (PCN)
2nd Mixer
PGA
I/Q demodulator
Tx block Offset PLL
I/Q modulator
Oscillator IF VCO
block
Divider (Rx)
Divider (Tx)
1st local buffer
IF local buffer
Total current
Receive
GSM
H
H
L
L
ON
OFF
ON
OFF
ON
ON
ON
OFF
OFF
ON
ON
OFF
ON
ON
53 mA
PCN
H
H
L
H
OFF
ON
OFF
ON
ON
ON
ON
OFF
OFF
ON
ON
OFF
ON
ON
52 mA
Calibrate
—
L
H
L
Don’t care
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
ON
ON
OFF
ON
ON
34 mA
Warm-up
—
L
L
L
Don’t care
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
OFF
OFF
ON
ON
9.0 mA
Transmit
GSM
L
L
H
L
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
ON
ON
ON
36 mA
PCN
L
L
H
H
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
ON
ON
ON
37 mA
Idle
—
H
L
Don’t care
Don’t care
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
1 µA
10