ML2724

DS2724-F-03

FINAL DATASHEET

DECEMBER 2005 13

Example 13kHz Loop Filter

MODES OF OPERATION

There are three key modes of operation:

STANDBY:

All circuits powered down, except the control interface (Static CMOS)

RECEIVE:

Receiver circuits active

TRANSMIT:

Modulated RF output from IC

The two operational modes are RECEIVE and TRANSMIT, controlled by RXON. XCEN is the chip enable/disable

control pin, which sets the part in operational or STANDBY modes. The relationship between the parallel control lines

and the mode of operation of the IC is given in Table 1.

XCEN

RXON

MODE

FUNCTION

0

X

STANDBY

Control interfaces active, all other circuits powered down

1

1

RECEIVE

Receiver time slot

1

0

TRANSMIT

Transmit time slot

Table 1: Modes of Operation

MODE CONTROL

The ML2724 is intended for use in TDD and TDMA radios in battery-powered equipment. To minimize power

consumption it is designed to switch rapidly from a low power mode (STANDBY) to an active mode. The ML2724 can

also make a quick transition from receive to transmit for TDD operation. Prior to transmitting or receiving, time should

be allowed for the PLL to lock and for the filters to align. When the ML2724 is operated in single-carrier TDD mode, the

LO is automatically shifted by the second (low) IF frequency when the device is switched between RECEIVE and

TRANSMIT modes.

ML2724 carrier frequency can be changed (hopped) at any time, but is usually changed between transmissions. Carrier

frequency (channel) is modified in the ML2724 by writing a corresponding new value to the PLL frequency register

(Register 1)

RECEIVE

The ML2724 uses a double-conversion super-heterodyne receiver with a nominal second IF of 1.024MHz. The signal

flow in RECEIVE mode is from the RF input, through an RF down-conversion mixer and integrated IF filter, image reject

quadrature mixer, integrated Low IF filter, hard limiter, frequency to voltage converter, and data filter to the AOUT pin

and data slicer where the digital NRZ data is available at the DOUT pin. A 20dB step AGC extends the dynamic range

of the receiver. The ML2724 receive chain is a Low IF receiver using advanced integrated radio techniques to eliminate

external IF filters and minimize external RF filter requirements. The precision filtering and demodulation circuits give

improved performance over conventional radio designs using external filters while providing integration comparable to

advanced direct conversion radio designs.

33nF

150

Ω

220nF

RVVCO

QPO

VTUNE