LT5557 datasheet(7/16 Pages) LINER

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LT5557

5557fa

PI FU CTIO S

NC (Pins 1, 2, 4, 8, 13, 14, 16): Not Connected Internally.

These pins should be grounded on the circuit board for the

best LO-to-RF and LO-to-IF isolation.

RF (Pin 3): 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. If the

RF source is not DC blocked, then a series blocking

capacitor must be used. The RF input is internally matched

from 1.6GHz to 2.3GHz. Operation down to 400MHz or up

to 3.8GHz is possible with simple external matching.

EN (Pin 5): Enable Pin. When the input enable voltage is

higher than 2.7V, the mixer circuits supplied through Pins

6, 7, 10 and 11 are enabled. When the input voltage is less

than 0.3V, all circuits are disabled. Typical input current is

μA for EN = 3.3V and 0μA when EN = 0V. The EN pin

should not be left floating. Under no conditions should the

EN pin voltage exceed VCC + 0.3V, even at start-up.

VCC2 (Pin 6): Power Supply Pin for the Bias Circuits.

Typical current consumption is 3.3mA. This pin should be

externally connected to the VCC1 pin and decoupled with

1000pF and 1

μF capacitors.

VCC1 (Pin 7): Power Supply Pin for the LO Buffer Circuits.

Typical current consumption is 25.1mA. This pin should

be externally connected to the VCC2 pin and decoupled

with 1000pF and 1

μF capacitors.

GND (Pins 9, 12): Ground. These pins are internally

connected to the backside ground for improved isolation.

They should be connected to the RF ground on the circuit

board, although they are not intended to replace the

primary grounding through the backside contact of the

package.

IF–, IF+ (Pins 10, 11): Differential Outputs for the IF

Signal. An impedance transformation may be required to

match the outputs. These pins must be connected to VCC

through impedance matching inductors, RF chokes or a

transformer center tap. Typical current consumption is

26.6mA each (53.2mA total).

LO (Pin 15): Single-Ended Input for the Local Oscillator

Signal. This pin is internally connected to the primary side

of the LO transformer, which is internally DC blocked. An

external blocking capacitor is not required. The LO input is

internally matched from 1GHz to 5GHz. Operation down to

380MHz is possible with simple external matching.

Exposed Pad (Pin 17): Circuit Ground Return for the

Entire IC. This must be soldered to the printed circuit board

ground plane.

BLOCK DIAGRA

DOUBLE-BALANCED

MIXER

LIMITING

AMPLIFIERS

VCC2

VCC1

IF+

GND

EXPOSED

PAD

IF–

GND

5557 BD

BIAS

VREF

REGULATOR

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