7-113

Once the midpoint voltage has

been acquired, TCSET is then

forced to a 0, and the time con-

stant of the midpoint voltage

tracking circuit is increased by a

factor of 80. This effectively

freezes the midpoint voltage from

any variations due to normal data

transitions, but still allows for

some correction of frequency

drifts during the data burst.

The output of the data slicer

(DATOP) is a CMOS-compatible

bitstream. However, it is recom-

mended that an external NPN

amplifier stage be used to drive

the CMOS baseband processor, in

order to minimize the amount of

ground and supply currents in the

HPMX-5002 which might desensi-

tize the chip.

Figure 3. Typical HPMX-5002 Application with HPMX-5001 T/R Chip.

32/33

LC filter

Quad.

Network

Data

Filter

Data

Slicer

RX DATA

÷9

RSSI

÷9

Charge

Pump

RC filter

Lock

Det.

HPMX-5002

PFD FREQ. = 1.152 MHz

Gaussian LPF

LO2 = 103.68 MHz

TX Data

0: 893.376 MHz Rx

896.832 MHz Tx

9: 885.600 MHz Rx

889.056 MHz Tx

CERAMIC

TX FILTER

TX PA

T/R

RX LNA

D: 1897.344 MHz

B: 1881.792 MHz

FRONT-END

RF FILTER

Tank

÷N

÷12

φ

Freq.

Det.

φ

Freq.

Det.

CERAMIC

IMAGE

FILTER

HPMX-5001

IF1 = 110.592 MHz

SAW Channel Filter

IF2 = 6.912 MHz

LC Filter

X2

10.368 MHz

REFERENCE

OSCILLATOR

SYNTHESIZER

N=1034 -1025 INCL. /32,33 Rx

N=1038 -1029 INCL. /32,33 Tx

PFD FREQ. = 864 kHz

Tank

All other connections go to Burst Mode Controller, power source, or ground.