4

LTC1757A-1/LTC1757A-2

TYPICAL PERFOR A CE CHARACTERISTICS

RF Detector Characteristics

at 1800MHz

RF INPUT POWER (dBm)

10

100

1000

10000

–22

–14 –10 –6

–2

2

6

10

1

–18

14

1757A G02

–30

°C

75

°C

25

°C

be bypassed with 0.1

µF and 100pF ceramic capacitors.

Used as return for RF 185

Ω termination.

RF (Pin 2): RF Feedback Voltage from the Directional

must be used to connect to the ground referenced direc-

tional coupler. The frequency range is 850MHz to 2000MHz.

This pin has an internal 185

Ω termination, an internal

Schottky diode detector and peak detector capacitor.

SHDN (Pin 3): Shutdown Input. A logic low on the SHDN

pin places the part in shutdown mode. A logic high places

the part in autozero when TXEN is low. SHDN has an inter-

nal 150k pull-down resistor to ensure that the part is in shut-

down when the drivers are in a three-state condition.

resistor to ground.

GND (Pin 5/Pin 4): System Ground.

PCTL (Pin 6/Pin 5): Analog Input. The external power

control DAC drives this input. The amplifier servos the RF

power until the RF detected signal equals the DAC signal.

The input resistance is typically 100k.

TXEN (Pin 7/Pin 6): Transmit Enable Input. A logic high

enables the control amplifier. When TXEN is low and

SHDN is high the part is in the autozero mode. This input

has an internal 150k resistor to ground.

Output. This pin drives an external RF power amplifier

power control pin. The maximum load capacitance is

100pF. The output is capable of rail-to-rail swings at low

load currents. Selected when BSEL is high.

drives an external RF power amplifier power control pin.

The maximum load capacitance is 100pF. The output is

capable of rail-to-rail swings at low load currents. Selected

when BSEL is low (LTC1757A-2 only).

has an internal 0.050

detect overcurrent conditions.

(LTC1757A-2/LTC1757A-1)

RF Detector Characteristics

at 900MHz

PI FU CTIO S

RF INPUT POWER (dBm)

10

100

1000

10000

–24

–12

–16

–8 –4

8

4

012

1

–20

16

1757A G01

–30

°C

75

°C

25

°C