LTC5542
8
5542f
PIN FUNCTIONS
NC (Pin 1): This pin is not connected internally. It can be
left fl oating, connected to ground or to V
CC
.
RF (Pin 2): Single-Ended Input for the RF Signal. This pin
is internally connected to the primary side of the RF input
transformer, which has low DC resistance to ground. A
series DC-blocking capacitor should be used to avoid
damage to the integrated transformer. The RF input is
impedance matched, as long as the selected LO input is
driven with a 0dBm ±6dB source between 1.7GHz and
2.5GHz.
CT (Pin 3): RF Transformer Secondary Center-Tap. This
pin may require a bypass capacitor to ground. See the
Applications Information section. This pin has an internally
generated bias voltage of 1.2V. It must be DC-isolated
from ground and V
CC
.
GND (Pins 4, 10, 12, 13, 17, Exposed Pad Pin 21):
Ground. These pins must be soldered to the RF ground
plane on the circuit board. The exposed pad metal of the
package provides both electrical contact to ground and
good thermal contact to the printed circuit board.
SHDN (Pin 5): Shutdown Pin. When the input voltage is
less than 0.3V, the internal circuits supplied through pins
6, 8, 14, 18 and 19 are enabled. When the input voltage
is greater than 3V, all circuits are disabled. Typical input
current is less than 10A. This pin must not be allowed
to fl oat.
V
CC2
(Pin 6) and V
CC1
(Pin 8): Power Supply Pins for
the LO Buffer and Bias Circuits. These pins are internally
connected and must be externally connected to a regulated
3.3V supply, with bypass capacitors located close to the
pin. Typical current consumption is 99mA.
LOBIAS (Pin 7): This Pin Allows Adjustment of the LO
Buffer Current. Typical DC voltage is 2.2V.
LOSEL (Pin 9): LO1/LO2 Select Pin. When the input voltage
is less than 0.3V, the LO1 port is selected. When the input
voltage is greater than 3V, the LO2 port is selected. Typical
input current is 11A for LOSEL = 3.3V. This pin must not
be allowed to fl oat.
LO1 (Pin 11) and LO2 (Pin 15): Single-Ended Inputs for
the Local Oscillators. These pins are internally biased
at 0V and require external DC blocking capacitors. Both
inputs are internally matched to 50, even when the chip
is disabled (SHDN = high).
V
CC3
(Pin 14): Power Supply Pin for the LO Switch. This
pin must be connected to a regulated 3.3V supply and
bypassed to ground with a capacitor near the pin. Typical
DC current consumption is less than 100A.
IFGND (Pin 16): DC Ground Return for the IF Amplifi er.
This pin must be connected to ground to complete the
IF amplifi er’s DC current path. Typical DC current is
100mA.
IF
–
(Pin 18) and IF
+
(Pin 19): Open-Collector Differential
Outputs for the IF Amplifi er. These pins must be connected
to a DC supply through impedance matching inductors, or
a transformer center-tap. Typical DC current consumption
is 50mA into each pin.
IFBIAS (Pin 20): This Pin Allows Adjustment of the IF
Amplifi er Current. Typical DC voltage is 2.1V.
