
For assistance or to order, call (800) 531-5782
78ST100 Series
1.5 AMP POSITIVE STEP-DOWN 
INTEGRATED SWITCHING REGULATOR
Revised 6/30/98
Standard Application
Vin
C1
1
78ST100
2
C1 = Optional 1µF ceramic 
C2 = Required 100µF electrolytic
• Very Small Footprint
• High Efficiency > 85%
• Self-Contained Inductor
• Internal Short-Circuit Protection
• Over-Temperature Protection
• Fast Transient Response
• Wide Input Range
The 78ST100 is a series of wide input 
voltage, 3-terminal Integrated Switching 
Regulators (ISRs). These ISRs have a maximum output current of 1.5A and an output 
voltage that is laser trimmed to a variety of 
industry standard voltages.
These 78 series regulators have excellent 
line and load regulation with internal shortcircuit and over-temperature protection, are 
very flexible, and may be used in a wide 
variety of applications.
Pin-Out Information
Pin Function
1V
in
2 GND 
3V
out
C2
Vout
+
GNDGND
3
Ordering Information
   78ST1
Output Voltage
33 = 3.3 Volts 
36 = 3.6 Volts 
05 = 5.0 Volts 
51 = 5.1 Volts 
65 = 6.5 Volts 
07 = 7.0 Volts 
08 = 8.0 Volts 
09 = 9.0 Volts 
12 = 12.0 Volts
        C
XX Y
Package Suffix
V = Vertical Mount 
S = Surface Mount 
H = Horizontal
    Mount
Specifications
Characteristics 
(Ta = 25°C unless noted) Symbols Conditions Min Typ Max Units
Output Current I 
Short Circuit Current I 
Input Voltage Range V
Output Voltage Tolerance ∆V
Line Regulation Reg 
Load Regulation Reg
Ripple/Noise V
V
o
Transient Response t 
 (with 100µF output cap) Vo over/undershoot — 5 — %V
Efficiency η V
Switching Frequency ƒ 
Absolute Maximum T
Operating Temperature Range 
Recommended Operating T
Temperature Range At Vin= 24V, Io=1.0A 
Thermal Resistance θ 
Storage Temperature T 
Mechanical Shock — Per Mil-STD-883D, Method 2002.3 — 500 — G’s 
Mechanical Vibration — Per Mil-STD-883D, Method 2007.2,
Weight — — — 6.5 — grams
*ISR will operate down to no load with reduced specifications. **See Thermal Derating chart.
Note: 
The 78ST100 Series requires a 100µF electrolytic or tantalum output capacitor for proper operation in all applications.
o
sc
in
o
line
load
n
tr
o
a
a
ja
s
Pkg Style 500
78ST100 SERIES
Over Vin range 0.1* — 1.5 A
Vin = V
min — 3.5 — Apk
in 
0.1 ≤ Io ≤ 1.5A Vo= 3.3V 7 — 26 V
Over Vin range, Io=1.5A
Ta = 0°C to +60°C
Over Vin range — ±0.2 ±0.4 %V
0.1 ≤ Io ≤ 1.5A — ±0.1 ±0.2 %V 
Vin= 9V, Io= 1.5A Vo= 5V — 65 — mV
Vin= 16V, Io= 1.5A Vo= 12V 90 mV 
50% load change — 100 — µSec
= 10V, Io= 1A Vo= 3.3V — 80 — %
in
V
= 10V, Io= 1A Vo= 5V — 85 — %
in
Vin= 17V, Io= 1A Vo= 12V — 90 — % 
Over Vin range, Io=1.5A 600 650 700 kHz 
—
Free Air Convection, (40-60LFM)
Free Air Convection, (40-60LFM) — 45 — °C/W 
— -40 — +125 °C
20-2000 Hz, soldered in a PC board
= 5V 7 — 30 V
V
o
Vo= 12V 14.5 — 30 V
— ±1.0 ±2.0 %V
-40 — +85 °C
-40 — +80** °C
—5
—
G’s
o
o 
o
pp 
pp
o
2
Power Trends, Inc. 27715 Diehl Road, Warrenville, IL 60555  (800) 531-5782  Fax: (630) 393-6902 http://www.powertrends.com
 

CHARACTERISTIC DATA
For assistance or to order, call (800) 531-5782
78ST100 Series
78ST133_  3.3 VDC   (See Note 1)
78ST105_  5.0 VDC (See Note 1)
Efficiency vs Output Current Efficiency vs Output Current
100
90
80
70
60
Efficiency (%)Ripple (mV)Iout (A)Pd (Watts)
50
40
0.0 0.5 1.0 1.5
Iout (A)
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
100
90
80
70
60
Efficiency (%)
50
40
0.0 0.5 1.0 1.5
Iout (A)
Ripple vs Output Current Ripple vs Output Current
60
50
40
30
20
10
0
0.0 0.5 1.0 1.5
Iout (A)
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
80
70
60
50
40
30
Ripple (mV)
20
10
0
0.0 0.5 1.0 1.5
Iout (A)
78ST112_  12.0 VDC  (See Note 1)
DATA SHEETS
Efficiency vs Output Current
100
90
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
80
70
60
Efficiency (%)
50
40
0.0 0.5 1.0 1.5
Vin
14.0V
20.0V
25.0V
30.0V
35.0V
Iout (A)
Ripple vs Output Current
140
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
120
100
80
60
Ripple (mV)Iout (A)
40
20
0
0.0 0.5 1.0 1.5
Iout (A)
Vin
14.0V
20.0V
25.0V
30.0V
35.0V
Thermal Derating (Ta)   (See Note 2) Thermal Derating (Ta)   (See Note 2)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
9 13172125
85°C
60°C
70°C
1.6
1.4
1.2
1
0.8
Iout (A)
0.6
0.4
0.2
0
9 12151821242730333639
60°C
70°C
85°C
Thermal Derating (Ta)   (See Note 2)
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
85°C
16 19 22 25 28 31 34 37 40
Vin (Volts)
Power Dissipation vs Output Current Power Dissipation vs Output Current
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.0 0.5 1.0 1.5
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
1.8
1.6
1.4
1.2
1.0
0.8
Pd (Watts)
0.6
0.4
0.2
0.0
0.0 0.5 1.0 1.5
Vin
7.0V
10.0V
15.0V
20.0V
25.0V
30.0V
Power Dissipation vs Output Current
2.5
2.0
1.5
1.0
Pd (Watts)
0.5
0.0
0.0 0.5 1.0 1.5
Iout (A) Iout (A) Iout (A)
Note 1: All data listed in the above graphs, except for derating data, has been developed from actual products tested at 25°C. This data is considered typical data for the ISR. 
Note 2: Thermal derating graphs are developed in free air convection cooling of 40-60 LFM. (See Thermal Application Notes.)
60°C
70°C
Vin (Volts)Vin (Volts)
Vin
14.0V
20.0V
25.0V
30.0V
35.0V
Power Trends, Inc. 27715 Diehl Road, Warrenville, IL 60555  (800) 531-5782  Fax: (630) 393-6902 http://www.powertrends.com
3
 

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