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Am79M535 Data Sheet

PIN DESCRIPTIONS

Pin Names

Type

Description

AGND

Gnd

Analog (quiet) ground

DGND

Gnd

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.

CHCLK

Input

Chopper Clock. Input to switching regulator (TTL compatible). Freq = 256 kHz (Nominal).

CHS

Input

Chopper stabilization. Connection for external stabilization components.

DA

Input

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

DB

Input

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

DET

Output

Detector. When enabled, logic Low indicates that the selected detector is tripped. Logic

inputs C3–C1, E1, and E0 select the detector. Open-collector with a built-in 15 k

Ω pull-

up resistor.

E0

Input

Read Enable. A logic Low disables DET. A logic High enables DET.

E1

Input

Ground-Key Enable. When E0 is High, E1 = High connects the ground-key detector to

DET, and E1 = Low connects the off-hook or ring-trip detector to DET.

GKFIL

Capacitor

Ground-Key Filter Capacitor Connection. An external capacitor for filtering out high-

frequency noise from the ground-key loop can be connected to this pin. An internal

36 k

Ω –20%, +40% resistor is provided to form an RC filter with the external capacitor.

In versions which have a GKFIL pin, a 3.3 nF minimum capacitance must be

connected from the GKFIL pin to ground.

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.

L

Output

Switching Regulator Power Transistor. Connection point for filter inductor and anode of

catch diode. Has up to 60 V of pulse waveform on it and must be isolated from sensitive

circuits. Keep the diode connections short because of the high currents and high di/dt

QBAT

Battery

Quiet Battery. Filtered battery supply for the signal processing circuits.

RD

Resistor

Detector 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

negative for normal polarity and positive for reverse polarity.

RINGOUT

Output

RSN

Input

The metallic current (AC and DC) between A(TIP) and B(RING) is equal to 1000 x the

current into this pin. The networks that program receive gain, two-wire impedance, and

feed current all connect to this node. This node is extremely sensitive. Route the 256 kHz

chopper clock and switch lines away from the RSN node.

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

Connected to office battery supply through an external protection diode.

VCC

Power

+5 V power supply

VEE

Power

–5 V power supply

VREG

Input

Regulated Voltage. Provides negative power supply for power amplifiers, connection

point for inductor, filter capacitor, and chopper stabilization.

VTX

Output

Transmit Audio. This output is 0.510 times the A(TIP) and B(RING) metallic voltage. VTX

also sources the two-wire input impedance programming network.