Device
Temperature
Range
Package
A78S40
SEMICONDUCTOR
TECHNICAL DATA
UNIVERSAL
SWITCHING REGULATOR
SUBSYSTEM
ORDERING INFORMATION
A78S40PC
A78S40PV
TA = 0
to +70
C
TA = 40
to +85
C
Plastic
Plastic
PIN CONNECTIONS
Order this document
A78S40/D
P SUFFIX
PLASTIC PACKAGE
CASE 648
11
5
2
1
9
10
12
13
14
15
16
8
7
6
4
3
(Top View)
Diode Anode
Reference
Inv. Input
Noninv.
VCC Op Amp
Op Amp Output
Switch Emitter
Diode Cathode
Op
Amp
Comparator
Noninv. Input
Comparator
Inv. Input
Ground
Timing Capacitor
VCC
Ipk Sense
Driver Collector
Switch Collector
1
MOTOROLA ANALOG IC DEVICE DATA
Universal Switching
Regulator Subsystem
The
A78S40 is a switching regulator subsystem, consisting of a
temperature compensated voltage reference, controlledduty cycle
oscillator with an active current limit circuit, comparator, highcurrent and
highvoltage output switch, capable of 1.5 A and 40 V, pinnedout 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 widesupply voltage
range, low standby current, high efficiency and low drift. The
A78S40 is
available in commercial (0
to + 70
C), and automotive (40
to + 85
C)
temperature ranges.
Some of the applications include use in stepup, stepdown, 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
Simplified Block Diagram
CT
Ipk
Oscilator
+
Comp.
+
Op
1.25V
Reference
S
R
Q
170
8
(Bottom View)
Ref
Output
Output
9
D1
Inv
Input
Noninv
Input
VCC
Op Amp
Switch
Emitter
Diode
Anode
Diode
Cathode
Noninv.
Input
Inv.
Input
Gnd
Timing
Capacitor
VCC
Ipk
Sense
Driver
Collector
Switch
Collector
7
6
5
4
3
2
1
10
11
12
13
14
15
16
Amp
Motorola, Inc. 1996
Rev 1
A78S40
2
MOTOROLA ANALOG IC DEVICE DATA
MAXIMUM RATINGS
Rating
Symbol
Value
Unit
Power Supply Voltage
VCC
40
V
Op Amp Power Supply Voltage
VCC (Op Amp)
40
V
Common Mode Input Range
(Comparator and Op Amp)
VICR
0.3 to VCC
V
Differential Input Voltage (Note 2)
VID
30
V
Output Short Circuit Duration (Op Amp)
Continuous
Reference Output Current
Iref
10
mA
Voltage from Switch Collectors to Gnd
40
V
Voltage from Switch Emitters to Gnd
40
V
Voltage from Switch Collectors to Emitter
40
V
Voltage from Power Diode to Gnd
40
V
ReversePower Diode Voltage
VDR
40
V
Current through Power Switch
ISW
1.5
A
Current through Power Diode
ID
1.5
A
Power Dissipation and Thermal Characteristics:
Plastic Package (TA = + 25
C)
Derate above + 25
C (Note 1)
PD
1/R
JA
1500
14
mW
mW/
C
Storage Temperature Range
Tstg
65 to + 150
C
Operating Temperature Range
A78S40V
A78S40C
TA
40 to +85
0 to +70
C
NOTES: 1. Tlow = 40
for
A78S40PV
Thigh = +85
for
A78S40PV
= 0
for
A78S40PC
= +70
for
A78S40PC
2. For supply voltages less than 30 V the maximum differential input voltage (Error Amp
and Op Amp) is equal to the supply voltage.
ELECTRICAL CHARACTERISTICS
(VCC = VCC (Op Amp) 5.0 V, TA = Tlow to Thigh, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
Unit
GENERAL
Supply Voltage
VCC
2.5
40
V
Supply Current (Op Amp VCC, disconnected)
(VCC = 5.0 V)
(VCC = 40 V)
ICC
1.8
2.3
3.5
5.0
mA
Supply Current (Op Amp VCC, connected)
(VCC = 5.0 V)
(VCC = 40 V)
ICC
4.0
5.5
mA
REFERENCE
Reference Voltage
(Iref = 1.0 mA)
Vref
1.180
1.245
1.310
V
Reference Voltage Line Regulation
(3.0 V
VCC
40 V, Iref = 1.0 mA, TA = 25
C)
Regline
0.04
0.2
mV/V
Reference Voltage Load Regulation
(1.0 mA
Iref
10 mA, TA = 25
C)
Regload
0.2
0.5
mV/mA
A78S40
3
MOTOROLA ANALOG IC DEVICE DATA
ELECTRICAL CHARACTERISTICS
(VCC = VCC (Op Amp) 5.0 V, TA = Tlow to Thigh, unless otherwise noted.)
Characteristic
Symbol
Min
Typ
Max
Unit
OSCILLATOR
Charging Current (TA = 25
C)
(VCC = 5.0 V)
(VCC = 40 V)
Ichg
20
20
50
70
A
Discharging Current (TA = 25
C)
(VCC = 5.0 V)
(VCC = 40 V)
Idis
150
150
250
350
A
Oscillator Voltage Swing (TA = 25
C)
(VCC = 5.0 V)
Vosc
0.5
V
Ratio of Charge/Discharge Time
tchg/tdis
6.0
CURRENT LIMIT
CurrentLimit Sense Voltage (TA = 25
C)
(VCC Vlpk Sense)
VCLS
250
350
mV
OUTPUT SWITCH
Output Saturation Voltage 1
(ISW = 1.0 A, Pin 15 tied to Pin 16)
Vsat1
0.93
1.3
V
Output Saturation Voltage 2
(ISW = 1.0 A, I15 = 50 mA)
Vsat2
0.5
0.7
V
Output Transistor Current Gain (TA = 25
C)
(IC = 1.0 A, VCE = 5.0 V)
hFE
70
Output Leakage Current (TA = 25
C)
(VCE = 40 V)
IC(off)
10
nA
POWER DIODE
Forward Voltage Drop (ID = 1.0 A)
VD
1.25
1.5
V
Diode Leakage Current (TA = 25
C) (VDR = 40 V)
IDR
10
nA
COMPARATOR
Input Offset Voltage (VCM = Vref)
VIO
1.5
15
mV
Input Bias Current (VCM = Vref)
IIB
35
200
nA
Input Offset Current (VCM = Vref)
IIO
5.0
75
nA
Common Mode Voltage Range (TA = 25
C)
VICR
0
VCC 2.0
V
PowerSupply Rejection Ratio (TA = 25
C)
(3.0
VCC
40 V)
PSRR
70
96
dB
OUTPUT OPERATION AMPLIFIER
Input Offset Voltage (VCM = 2.5 V)
VIO
4.0
15
mV
Input Bias Current (VCM = 2.5 V)
IIB
30
200
nA
Input Offset Current (VCM = 2.5 V)
IIO
5.0
75
nA
Voltage Gain + (TA = 25
C)
(RL = 2.0 k
to Gnd, 1.0 V
VO
2.5 V)
AVOL+
25
250
V/mV
Voltage Gain (TA = 25
C)
(RL = 2.0 k
to VCC (Op Amp), 1.0 V
VO
2.5 V)
AVOL
25
250
V/mV
Common Mode Voltage Range (TA = 25
C)
VICR
0
VCC 2.0
V
Common Mode Rejection Ratio (TA = 25
C)
(VCM = 0 V to 3.0 V)
CMRR
76
100
dB
PowerSupply Rejection Ratio (TA = 25
C)
(3.0 V
VCC (Op Amp)
40 V)
PSRR
76
100
dB
Output Source Current (TA = 25
C)
ISource
75
150
mA
Output Sink Current (TA = 25
C)
ISink
10
35
mA
Slew Rate (TA = 25
C)
SR
0.6
V/
s
Output Low Voltage (TA = 25
C, IL = 5.0 mA)
VOL
1.0
V
Output High Voltage (TA = 25
C, IL = 50 mA)
VOH
VCC(Op Amp)
3.0
V
A78S40
4
MOTOROLA ANALOG IC DEVICE DATA
Figure 1. Output Switch On/Off Time
versus Oscillator Timing Capacitor
Figure 2. Standby Supply Current
versus Supply Voltage
Figure 3. EmitterFollower Configuration
Output Switch Saturation Voltage
versus Emitter Current
CT, OSCILLATOR TIMING CAPACITOR (nF)
0.1
1.0
10
100
, OUTPUT
SWITCH ON-OFF
TIME (
s
)
on-of
f
t
VCC = 5.0 V
Ipk(sense) = VCC
Pin 10 = Gnd
Pin 9 = Vref
ton
toff
VCC, SUPPLY VOLTAGE (V)
0
5.0
10
15
20
25
30
35
40
, SUPPL
Y
CURRENT
(mA)
CC
I
CT = 0.001
F
Ipk(sense) = VCC
Pin 3 = Gnd
IE, EMITTER CURRENT (A)
, SA
TURA
TION VOL
T
AGE
(V)
CE(sat)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
V
VCC = 5.0 V
Pins 14, 15, 16 = VCC
Pins 10, 12 = Gnd
Pin 9 = Vref
IC, COLLECTOR CURRENT (A)
, SA
TURA
TION VOL
T
AGE
(V)
CE(sat)
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
V
VCC = 5.0 V
Pin 14 = VCC
Pins 3, 10, 12 = Gnd
Pin 9 = Vref
Darlington Connection
Figure 4. CommonEmitter Configuration
Output Switch Saturation Voltage
versus Collector Current
1000
100
10
1.0
3.2
2.4
1.6
0.8
0
1.6
1.5
1.4
1.3
1.2
1.1
1.0
1.2
1.0
0.8
0.6
0.4
0.2
0
Forced Beta = 20
A78S40
5
MOTOROLA ANALOG IC DEVICE DATA
CT
Ipk
Oscilator
+
Comp.
+
Op
Amp
1.25V
Reference
S
R
Q
170
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
D1
Vout
5.0V/500mA
*
L
470
+
CO
R2
3.6k
R1
1N5822
+
100
CT
* Use external rectifier to increase circuit efficiency
1.2k
Vin
25V
470
pF
RSC
0.33
220
H
VCC
Figure 5. StepDown Converter
CT
Ipk
Oscilator
+
Comp.
+
Op
Amp
1.25V
Reference
S
R
Q
170
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
D1
Vout
28V/175mA
*
150
+
CO
R2
47k
R1
1N5822
+
100
CT
* Use external rectifier to increase circuit efficiency
22k
Vin
12V
1500
pF
RSC
0.22
VCC
Figure 6. StepUp Converter
170
H
L
180
A78S40
6
MOTOROLA ANALOG IC DEVICE DATA
CT
Ipk
Oscilator
+
Comp.
+
Op
Amp
1.25V
Reference
S
R
Q
170
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
D1
R1
1.5k
1N5822
+
100
CT
Vin
15V
1800
pF
RSC
0.30
50
H
L
100
Vout
15V/500mA
100
+
CO
R2
18k
VCC
270
D45H8
Figure 7. Inverting Converter
Design Formula Table
fmin
Vin(min) Vsat
Calculation
StepDown
StepUp
Inverting
ton
toff
Vout + VF
Vout VF Vin(min)
Vout + VF
Vin(min) Vsat Vout
Vin(min) Vsat
(ton + toff) max
fmin
I
fmin
I
I
CT
4 x 10 5 ton
4 x 10 5 ton
4 x 10 5 ton
Ipk(switch)
2 Iout(max)
ton toff
toff
ton + toff
toff
2 Iout(max)
2 Iout(max)
RSC
0.33
0.33
0.33
Ipk(switch)
Ipk(switch)
Ipk(switch)
L(min)
Vin(min) Vsat Vout
Vin(min) Vsat
Vin(min) Vsat
ton(max)
ton(max)
ton(max)
Ipk(switch)
Ipk(switch)
Ipk(switch)
CO
Ipk(switch) (ton + toff)
Iout ton
Iout ton
8 Vripple(pp)
Vripple
Vripple
Vsat = Saturation voltage of the output switch. VF = Forward voltage drop of the ringback rectifier.
The following power supply characteristics must be chosen:
Nominal input voltage. If this voltage is not constant, then use Vin(max) for stepdown and Vin(min) for stepup and inverting convertor.
Desired output voltage: Vout = 1.25
Desired output current.
Minimum desired output switching frequency at the selected values for Vin and IO.
Desired peaktopeak output ripple voltage. In practice, the calculated value will need to be increased due to the capacitor's equivalent series
resistance and board layout. The ripple voltage should be kept to a low value since it will directly effect the line and load regulation.
See Application Note AN920 for further information
for stepdown and stepup:
for inverting.
1
)
R2
R1
Vout
+
1.25 R2
R1
Vin
Vout
Iout
fmin
Vripple(pp)
A78S40
7
MOTOROLA ANALOG IC DEVICE DATA
OUTLINE DIMENSIONS
P SUFFIX
PLASTIC PACKAGE
CASE 64808
ISSUE R
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEADS WHEN
FORMED PARALLEL.
4. DIMENSION B DOES NOT INCLUDE MOLD FLASH.
5. ROUNDED CORNERS OPTIONAL.
A
B
F
C
S
H
G
D
J
L
M
16 PL
SEATING
1
8
9
16
K
PLANE
T
M
A
M
0.25 (0.010)
T
DIM
MIN
MAX
MIN
MAX
MILLIMETERS
INCHES
A
0.740
0.770
18.80
19.55
B
0.250
0.270
6.35
6.85
C
0.145
0.175
3.69
4.44
D
0.015
0.021
0.39
0.53
F
0.040
0.70
1.02
1.77
G
0.100 BSC
2.54 BSC
H
0.050 BSC
1.27 BSC
J
0.008
0.015
0.21
0.38
K
0.110
0.130
2.80
3.30
L
0.295
0.305
7.50
7.74
M
0
10
0
10
S
0.020
0.040
0.51
1.01
_
_
_
_
A78S40
8
MOTOROLA ANALOG IC DEVICE DATA
Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding
the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and
specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Motorola
data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals"
must be validated for each customer application by customer's technical experts. Motorola does not convey any license under its patent rights nor the rights of
others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other
applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury
or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola
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arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola
was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal
Opportunity/Affirmative Action Employer.
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A78S40/D
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