RX5000 datasheet(7/11 Pages) RFM

7 / 11 page

Peak Detector Timing

The Peak Detector attack time constant is set by the value of the ca-

pacitor at the PKDET pin. The attack time tPKA =CPKD/4167, where

tPKA is in µs and CPKD is in pF. The Peak Detector decay time con-

stant tPKD = 1000*tPKA.

Pulse Generator Timing

In the low data rate mode, the interval tPRI between the falling edge

of an ON pulse to the first RF amplifier and the rising edge of the

next ON pulse to the first RF amplifier is set by a resistor RPR be-

tween the PRATE pin and ground. The interval can be adjusted be-

tween 0.1 and 5 µs with a resistor in the range of 51 K to 2000 K.

The value of the RPR is given by:

RPR = 404* tPRI + 10.5, where tPRI is in µs, and RPR is in kilohms

In the high data rate mode (selected at the PWIDTH pin) the re-

ceiver RF amplifiers operate at a nominal 50%-50% duty cycle. In

this case, the period tPRC from the start of an ON pulse to the first

RF amplifier to the start of the next ON pulse to the first RF amplifier

is controlled by the PRATE resistor over a range of 0.1 to 1.1 µs us-

ing a resistor of 11 K to 220 K. In this case RPR is given by:

RPR = 198* tPRC - 8.51, where tPRC is in µs and RPR is in kilohms

In the low data rate mode, the PWIDTH pin sets the width of the ON

pulse to the first RF amplifier tPW1 with a resistor RPW to ground (the

ON pulse width to the second RF amplifier tPW2 is set at 1.1 times

the pulse width to the first RF amplifier in the low data rate mode).

The ON pulse width tPW1 can be adjusted between 0.55 and 1 µs

with a resistor value in the range of 200 K to 390 K. The value of

RPW is given by:

RPW = 404* tPW1 - 18.6, where tPW1 is in µs and RPW is in kilohms

However, when the PWIDTH pin is connected to Vcc througha1M

resistor, the RF amplifiers operate at a nominal 50%-50% duty cy-

cle, facilitating high data rate operation. In this case, the RF amplifi-

ers are controlled by the PRATE resistor as described above.

LPF Group Delay

The low-pass filter group delay is a function of the filter 3 dB band-

width, which is set by a resistor RLPF to ground at the LPFADJ pin.

The minimum 3 dB bandwidth fLPF = 1445/RLPF, where fLPF is in kHz,

and RLPF is in kilohms.

The maximum group delay tFGD = 1750/fLPF = 1.21*RLPF, where tFGD

is in µs, fLPF in kHz, and RLPF in kilohms.

RX5000 Datasheet(PDF) 7 Page - RF Monolithics, Inc