HA17432UPA Просмотр технического описания (PDF) - Renesas Electronics
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HA17432UPA Datasheet PDF : 18 Pages
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HA17431VPJ/PJ/PAJ/FPJ/FPAJ/PNAJ/UPA, HA17432UPA
Application Hints (cont.)
No.
Application Example
3 Single power supply inverting
comparator circuit
Vin
GND
VCC
RL
Rin
K
REF A
Vout
GND
Description
This is an inverting type comparator with an input threshold voltage
of approximately 2.5 V. Rin is the REF pin protection resistance,
with a value of several kΩ to several tens of kΩ.
RL is the load resistance, selected so that the cathode current IK ≥ 1
mA when Vout is low.
Condition Vin
C1
Less then 2.5 V
C2
2.5 V or more
Vout
IC
VCC (VOH)
OFF
Approx. 2 V (VOL) ON
4 AC amplifier circuit
Cf
Vin
Cin R3
VCC
RL
R1
Vout
K
REF A
R2
GND
Gain G = R1 (DC gain)
R2 // R3
1
Cutoff frequency fc =
2π Cf (R1 // R2 // R3)
This is an AC amplifier with voltage gain G = –R1 / (R2//R3). The
input is cut by capacitance Cin, so that the REF pin is driven by the
AC input signal, centered on 2.5 VDC.
R2 also functions as a resistance that determines the DC cathode
potential when there is no input, but if the input level is low and
there is no risk of Vout clipping to VCC, this can be omitted.
To change the frequency characteristic, Cf should be connected as
indicated by the dotted line.
5 Switching power supply error
This circuit performs control on the secondary side of a transformer,
amplification circuit
and is often used with a switching power supply that employs a
photocoupler for offlining.
Secondary
side GND
+ LED
–
(Note)
R4
V+
R3
R1
Cf
R2
V–
The output voltage (between V+ and V–) is given by the following
formula:
Vout ≅ 2.5 V × (R1 + R2)
R2
In this circuit, the gain with respect to the Vout error is as follows:
G = R2
(R1 + R2)
×
HA17431 open
loop gain
×
photocoupler
total gain
As stated earlier, the HA17431 open-loop gain is 50 to 60 dB.
Note: LED : Light emitting diode in photocoupler
R3 : Bypass resistor to feed IK(>Imin)
when LED current vanishes
R4 : LED protection resistance
REJ03D0892-0100 Rev.1.00 Apr 03, 2007
Page 12 of 17
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