SL1062A 查看數據表（PDF） - System Logic Semiconductor
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SL1062A Datasheet PDF : 9 Pages
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SL1062A
Vref is an internally generated temperature
compensated reference voltage of 3.7 V and R9 is an
external resistor connected between SLPE and VEE.
In normal use the value of R9 would be 20Ω.
Changing the value of R9 will also affect microphone
gain, DTMF gain, gain control characteristics,
sidetone level, maximum output swing on LN and the
DC characteristics (especially at the lower voltages).
Under
normal
conditions,
when
ISLPE>>ICC + 0.5 mA + Ip, the static behaviour of the
circuit is that of a 3.7 V regulator diode with an
internal resistance equal to that of R9. In the audio
frequency range the dynamic impedance is largely
determined by R1. Fig.2 shows the equivalent
impedance of the circuit.
Leq = C3 x R9 x RP
RP = 16.2 KΩ
Figure 2. Equivalent impedance circuit
At line currents below 9mA the internal reference
voltage is automatically adjusted to a lower value
(typically 1.6 V at 1 mA) This means that more sets
can be operated in parallel with DC line voltages
(excluding the polarity guard) down to an absolute
minimum voltage of 1.6 V.
At line currents below 9 mA the circuit has limited
sending and receiving levels. The internal reference
voltage can be adjusted by means of an external
resistor (RVA). This resistor when connected between
LN and REG will decrease the internal reference
voltage and when connected between REG and SLPE
will increase the internal reference voltage.
Microphone inputs MIC+ and MIC- and gain pins
GAS1 and GAS2
The circuit has symmetrical microphone inputs. Its
input impedance is 64 KΩ (2 x 32 KΩ) and its voltage
gain is typically 52 dB (when R7 = 68 KΩ, see
Figure 3). Dynamic, magnetic, piezo-electric or
electret (with built-in FET source followers) can be
used.
The gain of the microphone amplifier can be adjusted
between 44 dB and 52 dB to suit the sensitivity of
the transducer in use. The gain is proportional to the
value of R7 which is connected between GAS1 and
GAS2.
Stability is ensured by two external capacitors, C6
connected between GAS1 and SLPE and C8
connected between GAS1 and VEE. The value of C6
is 100 pF but this may be increased to obtain a first-
order low-pass filter. The value of C8 is 10 limes the
value of C6. The cut-off frequency corresponds to
the time constant R7 x C6.
Input MUTE
When MUTE is LOW or open circuit, the DTMF
input is enabled and the microphone and receiving
amplifier inputs are inhibited. The reverse is true
when MUTE is HIGH, MUTE switching causes only
negligible clicking on the line and earpiece output. If
the number of parallel sets in use causes a drop in
line current to below 6 mA the DTMF amplifier
becomes active independent to the DC level applied
to the MUTE input.
Dial-tone multi-frequency input DTMF
When the DTMF input is enabled dialling tones may
be sent on to the line. The voltage gain from DTMF
to LN is typically 25.5 dB (when R7 = 68 KΩ) and
varies with R7 in the same way as the microphone
gain. The signalling tones can be heard in the
earpiece at a low level (confidence tone).
Receiving amplifier IR, QR and GAR
The receiving amplifier has one input (IR) and a non-
inverting output (QR). The IR to QR gain is typically
31 dB (when R4 = 100 KΩ). It can be adjusted
between 20 and 31 dB to match the sensitivity of the
transducer in use. The gain is set with the value of
R4 which is connected between GAR and QR. The
overall receive gain, between LN and QR, is
calculated by subtracting the anti-sidetone network
attenuation (32 dB) from the amplifier gain. Two
external capacitors, C4 and C7, ensure stability. C4 is
normally 100 pF and C7 is 10 times the value of C4.
The value of C4 may be increased to obtain a first-
order low-pass filter. The cut-off frequency will
depend on the time constant R4 x C4.
The output voltage of the receiving amplifier is
specified for continuous-wave drive. The maximum
output voltage will be higher under speech
conditions where the peak to RMS ratio is higher.
SLS
System Logic
Semiconductor
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