SSM2165-1S-REEL7 Analog Devices Inc, SSM2165-1S-REEL7 Datasheet - Page 5

• Manufacturer Part Number: SSM2165-1S-REEL7
• Description: IC PREAMP AUDIO MONO AB 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Class ABr

Specifications of SSM2165-1S-REEL7

• Rohs Status: RoHS non-compliant
• Output Type: 1-Channel (Mono)
• Voltage - Supply: 4.5 V ~ 5.5 V
• Features: Microphone
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Max Output Power X Channels @ Load: -

1
APPLICATIONS INFORMATION
The SSM2165 is a complete microphone signal conditioning
system in a single integrated circuit. Designed primarily for
voiceband applications, this integrated circuit provides amplifi-
cation, rms detection, limiting, variable compression, and down-
ward expansion. The internal rms detector has a time constant
set by an external capacitor. An integral voltage-controlled
amplifier (VCA) provides up to 40 dB of gain in the signal path
with approximately 30 kHz bandwidth. The device operates on
a single 5 V supply, accepts input signals up to 1 V
duces output signal levels at limiting of 320 mV and 250 mV for
the SSM2165-1 and SSM2165-2 respectively, into loads > 5 k .
The SSM2165 contains an input buffer and automatic gain
control (AGC) circuit for audio and voice band signals. Circuit
operation is optimized by providing user-adjustable compression
ratio and time constant. A downward expansion (noise gating)
feature reduces background and circuit noise below 500 V.
The rotation point determines the output signal levels before
limiting (referred to the input), and is 40 mV for the SSM2165-1
and 100 mV for the SSM2165-2.
All signals are in rms volts or dBu (0 dBu = 0.775 V rms).
INPUT – dB
DOWNWARD
EXPANSION
REGION
DOWNWARD
EXPANSION
THRESHOLD
(NOISE GATE)
100
90
0%
10
V
DE
COMPRESSION
REGION
LIMITING
THRESHOLD
(ROTATION POINT)
T
C
R
COMP RATIO
V
V
20mV
A
AVG
L
IN
IN
1
10k
25 C
12.5mV (–1)
40mV (–2)
r
1
2.2 F
1
1:1
V
rp
10 s
LIMITING
REGION
VCA GAIN
1
, and pro-
THEORY OF OPERATION
Figure 2 illustrates the general transfer characteristic for the
SSM2165 where the output level in dBu is plotted as a function
of the input level in dBu (0 dBu = 0.775 V rms). For input
signals in the range of V
(Rotation Point) an “r” dB change in the input level causes a 1
dB change in the output level. Here, “r” is defined as the “com-
pression ratio.” The compression ratio may be varied from 1:1
(no compression) to over 15:1 via a single resistor, R
Input signals above V
sion ratio of approximately 10:1. This region of operation is the
“limiting region.” Varying the compression ratio has no effect
on the limiting region. The breakpoint between the compres-
sion region and the limiting region is referred to as the
“limiting threshold” or “rotation point,” and is different for the
SSM2165-1 and SSM2165-2, see Table I.
SSM2165
–1
–2
The term “rotation point” derives from the observation that
the straight line in the compression region “rotates” about this
point on the input/output characteristic as the compression ratio
is changed.
When the compression is set to 2:1, a –2 dB change of the input
signal level in the compression region causes –1 dB change of
the output level. Likewise, at 10:1 compression, a –10 dB change
of the input signal level in the compression region causes a –1 dB
change in the output level. The gain of the system with an input
signal level of V
and is different for the SSM2165-1 and SSM2165-2 (see Figures
1a and 1b). The “nominal gain” of the system is 18 dB for the
SSM2165-1, and 8 dB for the SSM2165-2. System gain is mea-
sured at V
Input signals below V
approximately 1:3. As a result, the gain of the system is small
for very small input signal levels below V
be quite large for input signals above V
expansion threshold, V
dash versions.
At limiting.
RP
Table I. Characteristics vs. Dash Number
and is (V
Rotation Point
40 mV (–25.7 dBu)
100 mV (–17.7 dBu)
100
0%
90
10
RP
is fixed regardless of the compression ratio,
OUT
DE
RP
DE
DE
are compressed with a fixed compres-
are downward expanded at a ratio of
– V
, is fixed at 500 V (–64 dBu) for both
T
C
R
COMP RATIO
V
V
200mV
A
IN
IN
AVG
L
(Downward Expansion) to V
IN
) in dB.
25 C
10k
400mV (–2)
125mV (–1)
2.2 F
Gain
18 dB
8 dB
1:1
DE
DE
, even though it may
. The downward
10 s
SSM2165
Output
320 mV (–6 dBu)
250 mV (–8 dBu)
COMP
RP
.