FUJITSU MB3788 - Manual (Page 13)

MB3788
13
■ ■ ■ ■ HOW TO SET OUTPUT CURRENT
The output circuit is configured in a push-pull type as shown in Figure 1. The ON current value of the output
current waveform shown in Figure 2 is a constant current and the OFF value set by RE is set by a time constant.
Each output current can be calculated from the following expression:
• ON current = 1.5/R
E
(A) (Output current setting pin voltage: V
E
≈
1.5 V)
• The OFF current time constant is proportional to the value of C
B
.
OFF current
setting part
R E
C B
Drive Tr
OFF
current
ON current
Output
current
0
ON current
OFF current
t
22 µ H
(5 V)
3
150 Ω
1000 pF
4 5
1
V CC
I out
1000 pF
10
µ
F
-IN1 (E)
8.2 k
Ω
-IN1 (C)
MB3788
2
Fig.1 Output Circuit Diagram Fig.2 Output Current Waveform
Fig.3 Output Pin Voltage and Current Waveforms (Channel 1) Fig.4 Measurement Circuit Diagram
V E
2.7 k
Ω
V out