BL34018 Datasheet PDF - SHANGHAI BELLING

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BL34018
SHANGHAI BELLING

Part Number BL34018
Description high quality hands free speakerphone system
Page 16 Pages


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BL34018
1. GENERAL DESCRIPTION
The BL34018 Speakerphone integrated circuit Incorporates the necessary amplifiers
attenuators and control functions to produce a high quality hands free speakerphone
systemInclude are a microphone amplifiera power audio amplifier for the speakertransmit and
receive attenuatorsa monitoring system for background sound leveland an attenuation control
system which responds to the relative transmit and receive levels as well as the background
levelAlso included are all necessary regulated voltages for both internal and external circuitry
allowing line-powered operation (no additional power supplies required)A chip select pin allows
the chip to be powered down when not in useA volume control function may be implemented
with an external potentiometerBL34018 applications include speakerphones for household and
business useintercom systemsautomotive telephonesand others
2. FEATURE
Voice switched speakerphone circuit.
All necessary level detection and attenuation controls for a hand-free telephone
included.
Background noise level monitoring with long time constant.
Background sound level compensation for transmit and receive levels as well as
the background level.
Wide operating dynamic range through signal compression.
On-chip supply and reference voltage regulation.
Power audio amplifier for typical 100mW output (into 25 ohms) with peak
limiting for speaker to minimize distortion.
Chip Select pin for active/stand by operation.
Linear Volume Control Function.
3. BLOCK DIAGRAM
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BL34018
4. PIN CONFIGURATIONS
Pin Name Description
1 RR A resistor to ground provides a reference current for the transmit and receive attenuators.
2 RTX A resistor to ground determines the nominal gain of the transmit attenuator. The transmit
channel gain is inversely proportional to the RTX resistance.
3 TXI Input to the transmit attenuator. Input resistance is nominally 5.0 k ohms.
4 TXO Output of the transmit attenuator. The TXO output signal drives the input of the transmit
level detector, as well as the external circuit which drives the telephone line.
5 TLI Input of the transmit level detector. An external resistor ac coupled to the TLI pin sets the
detection level. Decreasing this resistor increases the sensitivity to transmit channel
signals.
6 TLO Output of the transmit level detector. The external resistor and capacitor set the time the
comparator will hold the system in the transmit mode after speech ceases.
7 RLI Input of the receive level detector. An external resistor ac coupled to the RLI pin sets the
detection level. Decreasing this resistor increases the sensitivity to receive channel
signals.
8 RLO Output of the receive level detector. The external resistor and capacitor set the time the
comparator will hold the system in the receive mode after speech ceases.
9 MCI Microphone amplifier input. Input impedance is nominally 10 k ohms and the dc bias
voltage is approximately equal to VB.
10 MCO Microphone amplifier output. The mic amp gain is internally set at 34 dB (50V/V).
11 CP1 A parallel resistor and capacitor connected between this pin and VCC holds a voltage
corresponding to the background noise level. The transmit detector compares the CP1
voltage with the speech signal from CP2.
12 CP2 A capacitor at this pin peak detects the speech signals for comparison with the
background noise level held at CP1.
13 XDI Input to the transmit detector system. The microphone amplifier output is ac coupled to
the XDI pin through an external resistor.
14 SKG High current ground pin for the speaker amp output stage. The SKG voltage should be
within 10 mV of the ground voltage at Pin 22.
15 SKO Speaker amplifier output. The SKO pin will source and sink up to 100 mA when ac
coupled to the speaker. The speaker amp gain is internally set at 34 dB (50V/V).
16 V+
Input dc supply voltage. V+ can be powered from Tip and Ring if an ac decoupling
inductor is used to prevent loading ac line signals. The required V+ voltage is 6.0 to 11 V
(7.5 V nominal) at 7.0 mA.
17 AGC A capacitor from this pin to VB stabilizes the speaker amp gain control loop and
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BL34018
additionally controls the attack and decay time of this circuit. The gain control loop limits
the speaker amp input to prevent clipping at SKO. The internal resistance at the AGC pin
is nominally 110 k ohms.
18 Digital chip select input. When at a logic “0” (<0.7 V) the VCC regulator is enabled.
CS When at a logic “1” (>1.6 V), the chip is in the standby mode drawing 0.5 mA. An open
CS pin is a logic “0”. Input impedance is nominally 140 k ohms. The input voltage
should not exceed 11 V.
19 SKI Input to the speaker amplifier. Input impedance is normally 20 k ohms.
20 VCC A 5.4 V regulated output which powers all circuits except the speaker amplifier output
stage. VCC can be used to power external circuitry such as a microprocessor( 3.0 mA
max). A filter capacitor is required. The BL34018 can be powered by a separate regulated
supply by connecting V+ and VCC to a voltage between 4.5 V and 6.5 V while
maintaining CS at a logic “1”.
21 VB
An output voltage equal to approximately VCC/2 which serves as an analog ground for
the speakerphone system. Up to 1.5 mA of external load current may be sourced from VB.
Output impedance is 250 ohms. A filter capacitor is required.
Gnd Ground pin for the IC (except the speaker amplifier).
22
23 XDC Transmit detector output. A resistor and capacitor at this pin hold the system in the
transmit mode during pauses between words and phrases. When the XDC pin voltage
decays to ground the attenuators switch from the transmit mode to the idle mode. The
internal resistor at XDC is nominally 2.6 k ohms.
24 VLC Volume control input. Connecting this pin to the slider of a variable resistor provides
receive mode volume control. The VLC pin voltage should be less than or equal to VB.
25 ACF Attenuator control filter. A capacitor connected to this pin reduces noise transients as the
attenuator control switches levels of attenuation.
26 RXO Output of the receive attenuator. Normally this pin is ac coupled to the input of the
speaker amplifier.
27 RXI Input of the receive attenuator. Input impedance is nominally 5.0 k ohms.
28 RRX A resistor to ground determines the nominal gain of the receive attenuator. The receive
channel gain is directly proportional to the RRX resistance.
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5. ELECTRICAL CHARACTERISTICS (Refer to Figure 1)
BL34018
ABSOLUTE MAXIMUM RATINGS
(voltages referred to Pin 22) (TA = 25°C)
Parameter
Value
V+ Terminal Voltage (Pin 16)
+12, -1.0
CS (Pin 18)
+12, -1.0
Units
V
V
Speaker Amp Ground (Pin 14)
+3.0, -1.0
V
VLC (Pin 24)
VCC, -1.0
V
Storage Temperature
-65 to +150
°C
“Maximum Ratings”are those values beyong which the safety of the device cannot be
guaranteed, They are not meant to imply that the devices should be operated at these
limits. The “Electrical Characteristics” tables provide conditions for actual device
operation.
RECOMMENDED OPERATING CONDITIONS
Parameter
Value
V+ Terminal Voltage (Pin 16)
+6.0 to +11
CS (Pin 18)
0 to +11
ICC (Pin 20)
VLC (Pin 24)
Receive Signal (Pin 27)
Microphone Signal (Pin 9)
Speaker Amp Ground (Pin 14)
Ambient Temperature
0 to 3.0
0.55VB to VB
0 to 250
0 to 5.0
-10 to +10
-20 to +60
Units
V
V
mA
V
mVrms
mVrms
mVdc
°C
ELECTRICAL CHARACTERISTICS
Parameter
SUPPLY VOLTAGES
V+ Supply Current
V+ = 11V, Pin 18 = 0.7V
V+ = 11V, Pin 18 = 1.6V
VCC Voltage ( V+ = 7.5V)
Line Regulation (6.5V< V+ <11V)
Symbol
Pin Min Typ Max Units
IV+
VCC
VCC LN
16
-- -- 9.0
-- -- 800
20 4.9 5.4 5.9
-- 65 150
mA
uA
Vdc
mV
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Total 16 Pages
8/15/2006
Wrote by 2006



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