LM5010
High Voltage 1A Step Down Switching Regulator
General Description
The LM5010 Step Down Switching Regulator features all the
functions needed to implement a low cost, efficient, buck
bias regulator capable of supplying in excess of 1A load
current. This high voltage regulator contains an N-Channel
Buck Switch, and is available in thermally enhanced LLP-10
and TSSOP-14EP packages. The hysteretic regulation
scheme requires no loop compensation, results in fast load
transient response, and simplifies circuit implementation.
The operating frequency remains constant with line and load
variations due to the inverse relationship between the input
voltage and the on-time. The valley current limit detection is
set at 1.25A. Additional features include: V
CC
under-voltage
lockout, thermal shutdown, gate drive under-voltage lockout,
and maximum duty cycle limiter.
Features
n
Input Voltage Range: 8V to 75V
n
Valley Current Limit At 1.25A
n
Switching Frequency Can Exceed 1 MHz
n
Integrated N-Channel Buck Switch
n
Integrated Startup Regulator
n
No Loop Compensation Required
n
Ultra-Fast Transient Response
n
Operating Frequency Remains Constant With Load and
Line Variations
n
Maximum Duty Cycle Limited During Startup
n
Adjustable Output Voltage
n
Precision 2.5V Feedback Reference
n
Thermal shutdown
Typical Applications
n
High Efficiency Point-Of-Load (POL) Regulator
n
Non-Isolated Telecommunications Buck Regulator
n
Secondary High Voltage Post Regulator
n
Automotive Systems
Package
n
LLP-10 (4 mm x 4 mm)
n
TSSOP-14EP
n
Both Packages Have Exposed Thermal Pad For
Improved Heat Dissipation
20119943
Basic Stepdown Regulator
October 2004
LM5010
High
V
oltage
1A
Step
Down
Switching
Regulator
2004 National Semiconductor Corporation
DS201199
www.national.com
Connection Diagrams
20119902
20119903
Ordering Information
Order Number
Package Type
NSC Package Drawing
Supplied As
LM5010SD
LLP-10 (4x4)
SDC10A
1000 Units on Tape and Reel
LM5010SDX
LLP-10 (4x4)
SDC10A
3500 Units on Tape and Reel
LM5010MH
TSSOP-14EP
MXA14A
1000 Units on Tape and Reel
LM5010MHX
TSSOP-14EP
MXA14A
3500 Units on Tape and Reel
LM5010
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Pin Description
PIN NUMBER
NAME
DESCRIPTION
APPLICATION INFORMATION
LLP-10
TSSOP-14
1
2
SW
Switching Node
Internally connected to the buck switch source.
Connect to the inductor, free-wheeling diode, and
bootstrap capacitor.
2
3
BST
Boost pin for bootstrap capacitor
Connect a 0.022 F capacitor from SW to this pin.
The capacitor is charged from V
CC
via an internal
diode during each off-time.
3
4
I
SEN
Current sense
The re-circulating current flows through the internal
sense resistor, and out of this pin to the
free-wheeling diode. Current limit is nominally set at
1.25A.
4
5
S
GND
Sense Ground
Re-circulating current flows into this pin to the
current sense resistor.
5
6
RTN
Circuit Ground
Ground for all internal circuitry other than the current
limit detection.
6
9
FB
Feedback input from the
regulated output
Internally connected to the regulation and
over-voltage comparators. The regulation level is
2.5V.
7
10
SS
Softstart
An internal 11.5 A current source charges an
external capacitor to 2.5V, providing the softstart
function.
8
11
R
ON
/SD
On-time control and shutdown
An external resistor from V
IN
to this pin sets the
buck switch on-time. Grounding this pin shuts down
the regulator.
9
12
V
CC
Output from the startup regulator
Nominally regulates at 7.0V. An external voltage
(7.5V-14V) can be applied to this pin to reduce
internal dissipation. An internal diode connects V
CC
to V
IN
.
10
13
V
IN
Input supply voltage
Nominal input range is 8.0V to 75V.
1,7,8,14
NC
No connection.
No internal connection.
LM5010
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Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
to GND
76V
BST to GND
90V
SW to GND (Steady State)
-1.5V
BST to V
CC
76V
BST to SW
14V
V
CC
to GND
14V
S
GND
to RTN
-0.3V to +0.3V
SS to RTN
-0.3V to 4V
V
IN
to SW
76V
Current Out of I
SEN
See Text
All Other Inputs to GND
-0.3 to 7V
ESD Rating (Note 2)
Human Body Model
2kV
Storage Temperature Range
-55C to +150C
Lead Temperature (Soldering 4 sec) (Note 4)
260C
Operating Ratings
(Note 1)
V
IN
8V to 75V
Operating Junction Temperature
-40C to + 125C
Electrical Charateristics
Specifications with standard typeface are for T
J
= 25C, and those with boldface type apply over full Operating Junction
Temperature range. V
IN
= 48V, R
ON
= 200k
, unless otherwise stated (Note 5) and (Note 6).
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
CC
Regulator
V
CC
Reg
V
CC
regulated output
6.6
7
7.4
Volts
V
IN
- V
CC
I
CC
= 0 mA, F
S
<
200 kHz
7.5V
V
IN
8.0V
1.3
V
V
CC
output impedance
(0 mA
I
CC
5 mA)
V
IN
= 8.0V
V
IN
= 48V
140
2.5
V
CC
current limit (Note 3)
V
CC
= 0V
10
mA
UVLO
VCC
V
CC
under-voltage lockout
threshold
V
CC
increasing
5.8
V
UVLO
VCC
hysteresis
V
CC
decreasing
145
mV
UVLO
VCC
filter delay
100 mV overdrive
3
s
I
IN
operating current
Non-switching, FB = 3V
650
850
A
I
IN
shutdown current
R
ON
/SD = 0V
95
200
A
Switch Characteristics
Rds(on)
Buck Switch Rds(on)
I
TEST
= 200 mA
0.35
0.80
UVLO
GD
Gate Drive UVLO
V
BST
- V
SW
Increasing
3.0
4.3
5.0
V
UVLO
GD
hysteresis
440
mV
Softstart Pin
Pull-up voltage
2.5
V
Internal current source
11.5
A
Current Limit
I
LIM
Threshold
Current out of I
SEN
1
1.25
1.5
A
Resistance from I
SEN
to S
GND
130
m
Response time
150
ns
On Timer, R
ON
/SD Pin
t
ON
- 1
On-time
V
IN
= 10V, R
ON
= 200 k
2.1
2.75
3.4
s
t
ON
- 2
On-time
V
IN
= 75V, R
ON
= 200 k
290
390
490
ns
Shutdown threshold
Voltage at R
ON
/SD rising
0.35
0.65
1.1
V
Threshold hysteresis
Voltage at R
ON
/SD falling
40
mV
Off Timer
t
OFF
Off-time
265
ns
LM5010
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Electrical Charateristics
(Continued)
Specifications with standard typeface are for T
J
= 25C, and those with boldface type apply over full Operating Junction
Temperature range. V
IN
= 48V, R
ON
= 200k
, unless otherwise stated (Note 5) and (Note 6).
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Regulation and Over-Voltage Comparators (FB Pin)
V
REF
FB regulation threshold
SS pin = steady state
2.445
2.5
2.550
V
FB over-voltage threshold
2.9
V
FB bias current
1
nA
Thermal Shutdown
T
SD
Thermal shutdown
temperature
175
C
Thermal shutdown hysteresis
20
C
Thermal Resistance
JA
Junction to Ambient
SDC Package
MXA Package
40
40
C/W
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device
is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: The human body model is a 100pF capacitor discharged through a 1.5k
resistor into each pin.
Note 3: V
CC
provides bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.
Note 4: For detailed information on soldering plastic TSSOP and LLP packages refer to the Packaging Data Book available from National Semiconductor
Corporation.
Note 5: Typical specifications represent the most likely parametric norm at 25C operation.
Note 6: All limits are guaranteed. All electrical characteristics having room temperature limits are tested during production with T
A
= 25C. All hot and cold limits are
guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
LM5010
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