參數(shù)資料
型號： MC33121
廠商： Motorola, Inc.
英文描述： LOW VOLTAGE SUBSCRIBER LOOP INTERFACE CIRCUIT
中文描述： 低電壓用戶環(huán)路接口電路
文件頁數(shù)： 7/32頁
文件大?。?/td> 570K
代理商： MC33121
MC33121
MOTOROLA
7
PIN FUNCTION DESCRIPTION
Symbol
b l
Pin
Description
DIP
PLCC
VCC
EP
20
28
Connect to noise–free battery ground. Carries loop current and some bias currents.
19
27
Connect to the emitter of the PNP pass transistor.
BP
18
26
Connect to the base of the PNP pass transistor.
CP
17
24
Connect to TIP through a current limiting protection resistor (RC). CP is the noninverting
input to the internal transmit amplifier (Figure 28). Input impedance is 31 k
.
TSI
16
23
Sense input. Connect to TIP through a current limiting protection resistor (RS) which also
sets the longitudinal impedance. Input impedance is
100
to VCC.
VDD
15
22
Connect to a + 5.0 V,
±
10% supply, referenced to digital ground. Powers logic section and
provides some bias currents for the loop current drivers.
VDG
ST1
14
20
Digital Ground. Reference for ST1, ST2 and VDD. Connect to system digital ground.
Status Output (TTL/CMOS). Indicates hook switch status — high when on–hook, low when
off–hook, and pulse dialing information. Used with ST2 to indicate fault conditions.
13
18
ST2/PDI
12
17
Status output and an input (TTL/CMOS). As an output, ST2 can indicate hook status — Low
when on–hook, high when off–hook. Used with ST1 to indicate fault conditions. As an input,
it can be taken low (when off–hook) to deny subscriber loop current.
TXO
11
16
Transmit voltage output. Amplitude is
800
μ
A output current. DC referenced to VAG.
1/3 that across CP and CN. Nominally capable of
RXI
10
14
Receive current input. Current at this pin is multiplied by 102 at EP and EN to generate loop
current. RXI is a virtual ground at VAG level. Current flow is out of this pin.
VAG
9
13
Analog ground, reference for TXO and RXI. Connect to system analog ground. Current flow
is into this pin.
RFO
8
12
A resistor from this pin and RXI sets the maximum loop current and DC feed resistance.
Minimum resistor value is 3.3 k (see Figures 5 to 7).
CF
7
10
A low leakage capacitor between this pin and VAG provides DC and AC signal separation. A
series resistor is required for battery supply turn–on/off transient protection (Figure 4).
VQB
6
8
Quiet Battery. A capacitor between VQB and VCC filters noise and ripple from VEE, providing
a quiet battery source for the speech amplifiers. A series resistor is required for battery
supply turn–on/off transient protection (Figure 4).
RSI
5
7
Sense input. Connect to RING through a current limiting protection resistor which also sets
the longitudinal impedance. Input impedance is
100
to VQB.
CN
4
6
Connect to RING through a current limiting protection resistor. CN is the inverting input to
the internal transmit amplifier (Figure 28). Input impedance is 31 k
.
BN
3
4
Connect to the base of the NPN pass transistor.
EN
2
3
Connect to the emitter of the NPN pass transistor.
VEE
1
2
Connect to battery voltage (– 21.6 V to – 42 V).
(Pins 1, 5, 9, 11, 15, 19, 21, and 25 are not internally connected on the PLCC package.)
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