Figure 2 illustrates how the 722 can provide isolated input
power to the input stage of two 3650s connected in the two-
port configuration. Power for the output stage is provided by
the system +15V and –15V supplies. Input stages are iso-
lated from each other and from the system supply. In this
situation, the 722 input-to-output isolation specification ap-
plies to the amplifier input-to-output voltages, whereas the
channel-to-channel 722 specification applies to the voltage
existing between I/P Com #1 and I/P Com #2.
SHORT CIRCUIT PROTECTION
The circuit in Figure 3 may be added to the input of the 722
to protect it from damage in situations where too much
current is demanded from the outputs—such as a short
circuit from an output to its common. The circuit limits input
current to approximately 150mA for an input voltage of
15VDC (for ß of 2N2219 of 50).
+15V –15V
P+
+VO1
C1
+
R1
3.6kΩ
2N2219
V+
E
–VO1
+VO2
C2
VIN
O/P Com
IN4148
+15V
+VO1 P+
V–
100Ω
1Ω
–VO2
–
C
722
R1
C1
V+
E
–VO1
+VO2
C2
I/P
Com #1
VIN
Com
–VO2 V–
I/P
Com #2
722
FIGURE 3. Short-Circuit Protection.
+15V –15V
O/P Com
–15V
O/P Com
FIGURE 2. Two-Port Isolation with Two 3650s.
722
SBVS016A
7
www.ti.com
BB [ BURR-BROWN CORPORATION ]
