
Am79231 Data Sheet
15
SPECIFICATIONS
Target Specifications (See note 1)
No.
Item
Condition
Min
Typ
Max
Unit
Note
1
Two-wire loop voltage (in-
cluding offset)
Standby mode, open circuit,
|VBH| < 55 V
|VBH| > 55 V
Any Active mode (does not
include OHT),
RL = 600
, I
RSN
= 50
μ
A
OHT mode, RL = 600
I
RSN
= 20
μ
A
VBH
–
8
48
13.88
8.64
19.8
130
VBH
–
7
51
15
10.8
22
250
VBH
–
6
55.5
16.13
12.96
V
3
2
Feed resistance per leg at
pins AD & BD
Feed current limit
Standby mode
375
3
Feed current
Standby mode, RL = 600
Standby mode, RL = 2200
Standby mode
A to VBH
B to Ground
Low boundary
High boundary
Input high current
Input low current
Mid-level current
Input high voltage
Input low voltage
Input high current
Input low current
34
56
45
mA
IMT current
ILG current
44.6
μA
36
43
4
Ternary input voltage
boundaries for LD pin.
Mid-level input source
must be Vref.
CREF
–
1
108
47
51
0.6
V
V
μA
μA
μA
V
V
μA
μA
mV
mA
mA
—
—
—
—
3
5
Logic Inputs P1, P2, P3
2.0
10
50
0.8
6
7
8
9
VTX output offset
VREF input current
CREF input current
β
, DC Ratio of VSAB to
loop voltage:
V
V
SA
–
–
50
+50
VREF = 1.4 V
CREF = 3.3 V
Tj < 145
°
C, VSA
–
VSB = 22 V
.05
.09
3
3
0.0088
0.0097
0.0106
V/V
10
Fault Indicator Threshold
Voltage Output on IMT
TBD
CREF -
0.3 V
30
CREF
V
3
11
Gain from VLB pin to A or
B pin
VLB pin input current
ILOOP/IMT
ILONG/ILG
Input current, SA and SB
pins
K1
ISA/IMT
ISB/ILG
VSAB output offset
IMT output offset
ILG output offset
V/V
12
13
14
15
VLB = VREF
±
1 V
ILOOP = 10 mA
ILONG = 10 mA
Active modes
TBD
300
600
1.0
mA
A/A
A/A
275
560
325
640
3.0
μA
3
16
17
18
19
20
21
Incremental DC current gain
Disconnect, ISA = 2 mA
Disconnect, ISB = 2 mA
500
6
12
TBD
0
1
A/A
mV
mV
mV
-3
-1
3
3
β
V
SB
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=