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Am7945 Data Sheet

PIN DESCRIPTIONS

Pin Names

Type

Description

AGND/DGND

Gnd

Analog and digital ground

A(TIP)

Output

Output of A(TIP) power amplifier

BGND

Gnd

Battery (power) ground

B(RING)

Output

Output of B(RING) power amplifier

C3–C1

Input

Decoder. TTL compatible. C3 is MSB and C1 is LSB.

CAS

Capacitor

Anti-saturation pin for capacitor to filter reference voltage when operating in anti-saturation

region.

DA

Input

Ring-Trip Negative. Negative input to ring-trip comparator.

DB

Input

Ring-Trip Positive. Positive input to ring-trip comparator.

DET

Output

Switchhook Detector. When enabled, a logic Low indicates the selected detector is tripped.

The detect condition is selected by the logic inputs (C3–C1, E0, E1). The output is open-

collector with a built-in 15 k

Ω pull-up resistor.

E0

Input

Ground-Key Enable. A logic High enables DET. A logic Low disables DET (PLCC only).

E1

Input

Ground-Key Enable. E1 = Low connects the ground-key or ring-trip detector to DET. E1 =

High connects the off-hook or ring-trip detector to DET (PLCC only).

HPA

Capacitor

High-Pass Filter Capacitor. A(TIP) side of high-pass filter capacitor.

HPB

Capacitor

High-Pass Filter Capacitor. B(RING) side of high-pass filter capacitor.

RD

Resistor

Detect Resistor. Threshold modification and filter point for the off-hook detector.

RDC

Resistor

DC Feed Resistor. Connection point for the DC feed current programming network. The

for normal polarity and positive for reverse polarity.

RINGOUT

Output

Ring Relay Driver. Open-collector driver with emitter internally connected to BGND.

RSN

Input

Receive Summing Node. The metallic current (both AC and DC) between A(TIP) and

B(RING) is equal to 200 times the current into this pin. Networks that program receive gain,

two-wire impedance, and feed resistance all connect to this node.

TMG

—

Thermal Management. Connect an external resistor between this pin and the VBAT pin to

reduce on-chip power dissipation in the normal polarity, Active state only. See Table 2.

TP

Thermal

Thermal pin. Connection for heat dissipation. Internally connected to substrate (QBAT).

Leave as open circuit or connected to QBAT. In both cases, the TP pins can connect to an

area of copper on the board to enhance heat dissipation.

VBAT

Battery

Battery supply

VCC

Power

+5 V power supply

VEE

Power

–5 V power supply

VTX

Output

Transmit Audio. This output is a unity gain version of the A(TIP) and B(RING) metallic

voltage. VTX also sources the two-wire input impedance programming network.