PIN DESCRIPTIONS
Pin Names
AGND
A(TIP)
BGND
B(RING)
C3–C1
C4
CHCLK
CHS
DA
DB
DET
DGND
E0
E1
Type
Gnd
Output
Gnd
Output
Input
Input
Input
Input
Input
Input
Output
Gnd
Input
Input
Analog (quiet) ground.
Output of A(TIP) power amplifier.
Battery (power) ground.
Output of B(RING) power amplifier.
Decoder. TTL compatible. C3 is MSB and C1 is LSB.
Test relay driver command (Am79534). TTL compatible. A logic Low enables the driver.
Chopper clock. Input to switching regulator (TTL compatible). Frequency = 256 kHz (nominal).
Chopper stabilization. Connection for external stabilization components.
Ring-trip negative. Negative input to ring-trip comparator.
Ring-trip positive. Positive input to ring-trip comparator.
Detector. A logic Low indicates that the selected detector is tripped. The detector is selected by
the logic inputs (C3–C1, E0, and E1). The output is open-collector with a built-in 15 kΩ pull-up
resistor.
Digital ground.
Read enable. A logic High enables DET. A logic Low disables DET.
Ground-key enable. E1 = High connects the ground-key detector to DET, and E1 = Low connects
the off-hook or ring-trip detector to DET.
Ground-key filter capacitor connection ( Am79535). An external capacitor for filtering out
high-frequency noise from the ground-key loop can be connected to this pin. An internal 36 kΩ, –
20%, +40% resistor is provided to form an RC filter with the external capacitor. In versions that
have a GKFIL pin, 3.3 nF minimum capacitance must be connected from the GKFIL pin to ground.
High-pass filter capacitor; A(TIP) side of high-pass filter capacitor.
High-pass filter capacitor; B(RING) side of high-pass filter capacitor.
Switching regulator power transistor. Connection point for filter inductor and anode of catch diode.
This pin 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.
Quiet battery. Filtered battery supply for the signal processing circuits.
Detect resistor. Threshold modification and filter point for the off-hook detector.
DC feed resistor. Connection point for the DC feed-current programming network which also
connects to the Receiver Summing Node (RSN). V
RDC
is negative for normal polarity and
positive for reverse polarity.
Ring relay driver; sourcing from BGND with internal diode to QBAT.
Receive summing node. The metallic current ( AC and DC) between A(TIP) and B(RING) is equal
to 1000 times 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.
Test relay driver (Am79534); sourcing from BGND with internal diode to QBAT.
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.
Battery supply through an external protection diode.
+5 V power supply.
–5 V power supply.
Regulated voltage. Provides negative power supply for power amplifiers and connection point for
inductor, filter capacitor, and chopper stabilization.
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 connects here.
Description
GKFIL
Capacitor
HPA
HPB
L
QBAT
RD
RDC
RINGOUT
Capacitor
Capacitor
Output
Battery
Resistor
Resistor
Output
RSN
Input
TESTOUT
TP
VBAT
VCC
VEE
VREG
VTX
Output
Thermal
Battery
Power
Input
Input
Output
4
Am7953X Data Sheet
AMD [ ADVANCED MICRO DEVICES ]
