Fujitsu MB3788 manual HOW to SET Output Current, Off

MB3788

■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/RE (A) (Output current setting pin voltage: VE ≈ 1.5 V)

•The OFF current time constant is proportional to the value of CB.

			Drive Tr
		CB
OFF current					OFF
				current
	setting part

ONcurrent

RE VE

	ON current
Output	0
current
	OFF current
	t

Fig.1 Output Circuit Diagram Fig.2 Output Current Waveform

1000 pF					VCC
4	5		1
						Iout
MB3788		2
					1000 pF
		3
				150			Ω

		-IN1 (C)
	22 ∝H		(5 V)
	10 ∝F		8.2 kΩ
Vout

2.7 kΩ

-IN1 (E)

Fig.3 Output Pin Voltage and Current Waveforms (Channel 1) Fig.4 Measurement Circuit Diagram

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