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78S40 Datasheet PDF : 9 Pages
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µA78S40
Universal Switching
Regulator Subsystem
The µA78S40 is a switching regulator subsystem, consisting of a
temperature compensated voltage reference, controlled–duty cycle
oscillator with an active current limit circuit, comparator, high–current
and high–voltage output switch, capable of 1.5 A and 40 V, pinned–out
power diode and an uncommitted operational amplifier, which can be
powered up or down independent of the IC supply. The switching
output can drive external NPN or PNP transistors when voltages
greater the 40 V, or currents in excess of 1.5 A, are required. Some of
the features are wide–supply voltage range, low standby current, high
efficiency and low drift. The µA78S40 is available in commercial
(0° to + 70°C), and automotive (–40° to + 85°C) temperature ranges.
Some of the applications include use in step–up, step–down, and
inverting regulators, with extremely good results obtained in battery–
operated systems.
• Output Adjustable from 1.25 V to 40 V
• Peak Output Current of 1.5 A Without External Transistor
• 80 dB Line and Load Regulation
• Operation from 2.5 V to 40 V Supply
• Low Standby Current Drain
• High Gain, High Output Current, Uncommitted Op Amp
Noninv. Inv.
Input
Input
9
10
Timing
Gnd Capacitor VCC
11
12
13
Ipk
Sense
14
Driver
Collector
15
Switch
Collector
16
CT
Ipk
Oscillator
SQ
1.25V
Reference
-
+Comp.
- Op
Amp
+
R
170
D1
8
Ref
Output
7
6
5
4
3
2
1
Inv Noninv VCC Output Switch Diode Diode
Input Input Op Amp
Emitter Anode Cathode
(Bottom View)
This device contains 84 active transistors.
Figure 1. Simplified Block Diagram
16
1
http://onsemi.com
MARKING
DIAGRAM
16
PDIP–16
P SUFFIX
CASE 648
UA78S40Px
AWLYYWW
1
x = C or V
A = Assembly Location
WL = Wafer Lot
YY = Year
WW = Work Week
PIN CONNECTIONS
Diode Cathode 1
16 Switch Collector
Diode Anode 2
15 Driver Collector
Switch Emitter 3
14 Ipk Sense
Op Amp Output 4
VCC Op Amp 5
Op Noninv. 6
Amp Inv. Input 7
Reference 8
13 VCC
12 Timing Capacitor
11 Ground
10
Comparator
Inv. Input
9
Comparator
Noninv. Input
(Top View)
ORDERING INFORMATION
Device
Package
Shipping
µA78S40PC
PDIP–16
25 Units/Rail
µA78S40PV
PDIP–16
25 Units/Rail
© Semiconductor Components Industries, LLC, 2001
1
February, 2001 – Rev. 2
Publication Order Number:
µA78S40/D
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