NSC LM3578AM, LM2578AN, LM1578AH-883, LM3578AN Datasheet
LM1578A/LM2578A/LM3578A Switching Regulator
LM1578A/LM2578A/LM3578A Switching Regulator
April 1995
General Description
The LM1578A is a switching regulator which can easily be
set up for such DC-to-DC voltage conversion circuits as the
buck, boost, and inverting configurations. The LM1578A
features a unique comparator input stage which not only
has separate pins for both the inverting and non-inverting
inputs, but also provides an internal 1.0V reference to each
input, thereby simplifying circuit design and p.c. board layout. The output can switch up to 750 mA and has output
pins for its collector and emitter to promote design flexibility.
An external current limit terminal may be referenced to either the ground or the V
plication. In addition, the LM1578A has an on board oscillator, which sets the switching frequency with a single external capacitor from
terminal, depending upon the ap-
in
k
1 Hz to 100 kHz (typical).
The LM1578A is an improved version of the LM1578, offering higher maximum ratings for the total supply voltage and
output transistor emitter and collector voltages.
Functional Diagram
Features
Y
Inverting and non-inverting feedback inputs
Y
1.0V reference at inputs
Y
Operates from supply voltages of 2V to 40V
Y
Output current up to 750 mA, saturation less than 0.9V
Y
Current limit and thermal shut down
Y
Duty cycle up to 90%
Applications
Y
Switching regulators in buck, boost, inverting, and
single-ended transformer configurations
Y
Motor speed control
Y
Lamp flasher
TL/H/8711– 1
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
TL/H/8711
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Total Supply Voltage 50V
Collector Output to Ground
Emitter Output to Ground (Note 2)
Power Dissipation (Note 3) Internally limited
Output Current 750 mA
Storage Temperature
Lead Temperature
(soldering, 10 seconds) 260
b
0.3V toa50V
b
1V toa50V
b
65§Ctoa150§C
Maximum Junction Temperature 150
C
§
ESD Tolerance (Note 4) 2 kV
Operating Ratings
Ambient Temperature Range
LM1578A
LM2578A
b
55§CsT
b
40§CsT
LM3578A 0
Junction Temperature Range
LM1578A
C
§
LM2578A
LM3578A 0
b
55§CsT
b
40§CsT
CsT
§
CsT
§
s
a
125§C
A
s
a
85§C
A
s
a
70§C
A
s
a
150§C
J
s
a
125§C
J
s
a
125§C
J
Electrical Characteristics
These specifications apply for 2VsV
s
duty cycles75%, unless otherwise specified. Values in standard typeface are for T
for operation over the specified operating junction temperature range.
Symbol Parameter Conditions
s
40V (2.2VsV
IN
IN
s
40V for T
s
b
25§C), timing capacitor C
J
Typical
(Note 5)
e
J
LM1578A
(Notes 6, 11)
e
3900 pF, and 25%
25§C; values in boldface type apply
T
LM2578A/
Limit
LM3578A
Limit
(Note 7)
Units
OSCILLATOR
f
OSC
Frequency 20 kHz
22.4 24 kHz (max)
17.6 16 kHz (min)
Df
/DT Frequency Drift with
OSC
Temperature
Amplitude 550 mV
b
0.13 %/§C
p-p
REFERENCE/COMPARATOR (Note 8)
e
V
R
Input Reference I
Voltage I
DVR/DVINInput Reference Volt- I
age Line Regulation I
I
INV
Inverting Input I
Current
e
I
1
1
1
1
1
0 mA and 1.0 V
2
e
e
I
1mAg1% (Note 9) 1.035/1.050 1.050/1.070 V (max)
2
e
e
I
0 mA and 0.003 %/V
2
e
e
I
1mAg1% (Note 9) 0.01/0.02 0.01/0.02 %/V (max)
2
e
e
I
0 mA, duty cyclee25% 0.5 mA
2
0.965/0.950 0.950/0.930 V (min)
Level Shift Accuracy Level Shift Currente1 mA 1.0 %
5/8 10/13 % (max)
DVR/Dt Input Reference 100 ppm/1000h
Voltage Long Term
Stability
OUTPUT
VC(sat) Collector Saturation I
Voltage grounded 0.85/1.2 0.90/1.2 V (max)
VE(sat) Emitter Saturation I
Voltage V
I
CES
BV
CEO(SUS)
Collector Leakage V
Current grounded, Output OFF 50/100 200/250 mA (max)
Collector-Emitter I
Sustaining Voltage 50 50 V (min)
e
750 mA pulsed, Emitter 0.7 V
C
e
80 mA pulsed, 1.4 V
O
e
e
V
IN
IN
SUST
40V 1.6/2.1 1.7/2.0 V (max)
C
e
e
V
40V, Emitter 0.1 mA
CE
e
0.2A (pulsed), V
e
060 V
IN
2
Electrical Characteristics (Continued)
Symbol Parameter Conditions
Typical
(Note 5)
LM1578A
Limit
(Notes 6, 11)
CURRENT LIMIT
V
CL
Sense Voltage Referred to VINor Ground 110 mV
Shutdown Level (Note 10) 95 80 mV (min)
140 160 mV (max)
DVCL/DT Sense Voltage 0.3 %/§C
Temperature Drift
I
CL
Sense Bias Current Referred to V
Referred to ground 0.4 mA
IN
4.0 mA
DEVICE POWER CONSUMPTION
I
S
Supply Current Output OFF, V
Output ON, I
e
V
0V
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating
the device beyond its rated operating conditions.
Note 2: For T
Note 3: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the TO-99 package must be derated at 150
junction to ambient, or 45
package must be derated at 150
Note 4: Human body model, 1.5 kX in series with 100 pF.
Note 5: Typical values are for T
Note 6: All limits guaranteed and 100% production tested at room temperature (standard type face) and at temperature extremes (bold type face). All limits are
used to calculate Average Outgoing Quality Level (AOQL).
Note 7: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). Room temperature limits are 100%
production tested. Limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to
calculate AOQL.
Note 8: Input terminals are protected from accidental shorts to ground but if external voltages higher than the reference voltage are applied, excessive current will
flow and should be limited to less than 5 mA.
Note 9: I
Note 10: Connection of a 10 kX resistor from pin 1 to pin 4 will drive the duty cycle to its maximum, typically 90%. Applying the minimum Current Limit Sense
Voltage to pin 7 will not reduce the duty cycle to less than 50%. Applying the maximum Current Limit Sense Voltage to pin 7 is certain to reduce the duty cycle
below 50%. Increasing this voltage by 15 mV may be required to reduce the duty cycle to 0%, when the Collector output swing is 40V or greater (see Ground-Referred Current Limit Sense Voltage typical curve).
Note 11: A military RETS specification is available on request. At the time of printing, the LM1578A RETS spec complied with the boldface limits in this column.
The LM1578AH may also be procured as a Standard Military Drawing.
t
100§C, the Emitter pin voltage should not be driven more than 0.6V below ground (see Application Information).
J
C/W, junction to case. The device in the 8-pin DIP must be derated at 95§C/W, junction to ambient. The device in the surface-mount
§
C/W, junction-to-ambient.
§
e
J
and I2are the external sink currents at the inputs (refer to Test Circuit).
1
E
25§C and represent the most likely parametric norm.
e
0V 2.0 mA
E
e
750 mA pulsed, 14 mA
C
3.0/3.3 3.5/4.0 mA (max)
LM2578A/
LM3578A
Limit
(Note 7)
Units
§
C/W,
Connection Diagram and Ordering Information
Metal Can
Order Number LM3578AM, LM2578AN or LM3578AN
Order Number LM1578AH/883 or SMD
Top View
See NS Package Number H08C
TL/H/8711– 28
Ý
5962-8958602
3
Dual-In-Line Package
TL/H/8711– 29
See NS Package Number M08A or N08E
Typical Performance Characteristics
Oscillator Frequency Change
with Temperature
Collector Saturation Voltage
(Sinking Current,
Emitter Grounded)
Current Limit Sense Voltage
Drift with Temperature
Oscillator Voltage Swing Drift with Temperature
Emitter Saturation Voltage
(Sourcing Current,
Collector at V
Current Limit Response Time
for Various Over Drives
)
in
Input Reference Voltage
Ground Referred
Current Limit Sense Voltage
Current Limit Sense Voltage
vs Supply Voltage
Supply Current Supply Current Emitter Output Below Ground
4
Collector Current with
TL/H/8711– 2
Test Circuit*
Parameter tests can be made using the test circuit shown.
Select the desired V
adjustable power supplies. A digital volt meter with an input
resistance greater than 100 MX should be used to measure
the following:
Input Reference Voltage to Ground; S1 in either position.
Level Shift Accuracy (%)
e
e
I
I
1
2
Input Current (mA)
e
I
0 mA.
2
Oscillator parameters can be measured at T
quency counter or an oscilloscope.
, collector voltage and duty cycle with
in
e
(TP3(V)/1V)c100%; S1 at
1mA
e
(1VbTp3(V))/1 MX:S1atI
using a fre-
p4
1
e
The Current Limit Sense Voltage is measured by connecting
an adjustable 0-to-1V floating power supply in series with
the current limit terminal and referring it to either the ground
or the V
test point T
age until the LM1578A’s duty cycle just reaches 0%. This
terminal. Set the duty cycle to 90% and monitor
in
while adjusting the floating power supply volt-
P5
voltage is the Current Limit Sense Voltage.
The Supply Current should be measured with the duty cycle
at 0% and S1 in the I
e
e
I
1
0 mA position.
2
*LM1578A specifications are measured using automated
test equipment. This circuit is provided for the customer’s
convenience when checking parameters. Due to possible
variations in testing conditions, the measured values from
these testing procedures may not match those of the
factory.
Note 1: Op amp supplies areg15V
Note 2: DVM input resistance
Note 3: *LM1578 max duty cycle is 90%
l
100 MX
Definition of Terms
Input Reference Voltage: The voltage (referred to ground)
that must be applied to either the inverting or non-inverting
input to cause the regulator switch to change state (ON or
OFF).
Input Reference Current: The current that must be drawn
from either the inverting or non-inverting input to cause the
regulator switch to change state (ON or OFF).
Input Level Shift Accuracy: This specification determines
the output voltage tolerance of a regulator whose output
control depends on drawing equal currents from the inverting and non-inverting inputs (see the Inverting Regulator of
Figure 21
ure 23
, and the RS-232 Line Driver Power Supply of
Fig-
).
Level Shift Accuracy is tested by using two equal-value resistors to draw current from the inverting and non-inverting
input terminals, then measuring the percentage difference in
the voltages across the resistors that produces a controlled
duty cycle at the switch output.
TL/H/8711– 3
Collector Saturation Voltage: With the inverting input terminal grounded thru a 10 kX resistor and the output transistor’s emitter connected to ground, the Collector SaturationVoltage is the collector-to-emitter voltage for a given collector current.
Emitter Saturation Voltage: With the inverting input terminal grounded thru a 10 kX resistor and the output transistor’s collector connected to V
age is the collector-to-emitter voltage for a given emitter
, the Emitter Saturation Volt-
in
current.
Collector Emitter Sustaining Voltage: The collector-emitter breakdown voltage of the output transistor, measured at
a specified current.
Current Limit Sense Voltage: The voltage at the Current
Limit pin, referred to either the supply or the ground terminal, which (via logic circuitry) will cause the output transistor
to turn OFF and resets cycle-by-cycle at the oscillator frequency.
5
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