NSC LM3100MH, LM3100 Datasheet
LM3100
SIMPLE SWITCHER
®
Synchronous 1MHz 1.5A
Step-Down Voltage Regulator
LM3100 SIMPLE SWITCHER
February 2006
General Description
The LM3100 Synchronously Rectified Buck Converter features all functions needed to implement a highly efficient,
cost effective buck regulator capable of supplying 1.5A to
loads with voltages as low as 0.8V. Dual 40V N-Channel
synchronous MOSFET switches allow for low external component thus reducing complexity and minimizing board
space. The LM3100 is designed to work exceptionally well
with ceramic and other very low ESR output capacitors. The
Constant ON-Time (COT) regulation scheme requires no
loop compensation, results in fast load transient response,
and simplifies circuit implementation. Through the use of a
unique design the regulator does not rely on output capacitor
ESR for stability, as do most other COT regulators. The
operating frequency remains nearly constant with line and
load variations due to the inverse relationship between the
input voltage and the on-time. The oprating frequency can
be externally programmed up to 1MHz. Protection features
include V
gate drive under-voltage lockout. The part is available in a
thermally enhanced eTSSOP-20 package
under-voltage lockout, thermal shutdown and
CC
Features
n Input voltage range 4.5V - 36V
n 1.5A output current
n 0.8V,
n Integrated 40V, dual N-Channel buck synchronous
n Low component count and small solution size
n No loop compensation required
n Ultra-fast transient response
n Stable with ceramic and other low ESR capacitors
n Programmable switching frequency up to 1MHz
n Max. duty cycle limited during start-up
n Valley current limit
n Precision Internal Reference for adjustable output
n Thermal shutdown
n Thermally enhanced eTSSOP-20 package
±
1.5% reference
switches
voltage down to 0.8V
Typical Applications
n 5VDC, 12VDC, 24VDC, 12VAC, and 24VAC systems
n Embedded Systems
n Industrial Controls
n Automotive Telematics and Body Electronics
n Point of Load Regulators
n Storage Systems
n Broadband Infrastructure
n Direct Conversion from 2/3/4 Cell Lithium Batteries
Systems
®
Synchronous 1MHz 1.5A Step-Down Voltage Regulator
Typical Application
20174702
SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation
© 2006 National Semiconductor Corporation DS201747 www.national.com
Connection Diagram
LM3100
20-lead Plastic
eTSSOP (MXA20A)
20174703
Ordering Information
Order Number Package Type NSC Package Drawing Supplied As
LM3100MH Exposed Pad
LM3100MHX 2500 Units on Tape and Reel
TSSOP-20
MXA0020 73 units per Anti-Static Tube
www.national.com 2
Pin Descriptions
Pin Name Description Application Information
1,9,10,12,19,20 N/C No Connection These pins must be left unconnected.
2, 3 SW Switching Node Internally connected to the buck switch source.
Connect to output inductor.
4, 5 VIN Input supply voltage Supply pin to the device. Nominal input range is
4.5V to 36V.
6 BST Connection for bootstrap capacitor Connect a 0.033µF capacitor from SW pin to this
pin. An internal diode charges the capacitor during
the high-side switch off-time.
7 GND Analog Ground Ground for all internal circuitry other than the
synchronous switches.
8 SS Soft-start An internal 8µA current source charges an external
capacitor to provide the soft- start function.
11 TST Test mode enable pin Force the device into test mode. Must be connected
to ground for normal operation.
13 FB Feedback Internally connected to the regulation and
over-voltage comparators. The regulation setting is
0.8V at this pin. Connect to feedback divider.
14 EN Enable pin Connect a voltage higher than 1.26V to enable the
regulator.
15 RON On-time Control An external resistor from VIN to this pin sets the
high-side switch on-time.
16 VCC Start-up regulator Output Nominally regulated to 6V. Connect a capacitor of
not less than 680nF between VCC and GND for
stable operation.
17, 18 PGND Power Ground Synchronous rectifier MOSFET source connection.
Tie to power ground plane.
DAP EP Exposed Pad Thermal connection pad, connect to GND.
LM3100
www.national.com3
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM3100
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VIN, RON to GND -0.3V to 40V
SW to GND -0.3V to 40V
SW to GND (Transient) -2V (
VIN to SW -0.3V to 40V
BST to SW -0.3V to 7V
All Other Inputs to GND -0.3V to 7V
<
100ns)
ESD Rating (Note 2)
Human Body Model
±
2kV
Storage Temperature Range -65˚C to +150˚C
Junction Temperature (T
) 150˚C
J
Operating Ratings (Note 1)
Supply Voltage Range (VIN) 4.5V to 36V
Junction Temperature Range (T
Thermal Resistance (θ
) (Note 3) 6.5˚C/W
JC
) −40˚C to + 125˚C
J
Electrical Charateristics Specifications with standard type are for T
ply over the full Operating Junction Temperature (T
sign, or statistical correlation. Typical values represent the most likely parametric norm at T
erence purposes only. Unless otherwise stated the following conditions apply: V
) range. Minimum and Maximum limits are guaranteed through test, de-
J
= 25˚C only; limits in boldface type ap-
J
= 25˚C, and are provided for ref-
= 18V, V
IN
J
OUT
= 3.3V.
Symbol Parameter Conditions Min Typ Max Units
Start-Up Regulator, V
V
CC
V
IN-VCC
I
VCCL
V
CC-UVLO
CC
VCCoutput voltage CCC= 680nF, no load 5.0 6.0 7.2 V
VIN-VCCdropout voltage ICC= 2mA 50 140 mV
I
= 20mA 350 570
CC
VCCcurrent limit (Note 4) VCC=0V 40 65 mA
VCCunder-voltage lockout threshold
VINincreasing 3.6 3.75 3.85 V
(UVLO)
V
CC-UVLO-HYS
t
VCC-UVLO-D
I
IN
I
IN-SD
VCCUVLO hysteresis VINdecreasing 130 mV
VCCUVLO filter delay 3 µs
IINoperating current No switching, VFB= 1V 0.7 1 mA
IINoperating current, Device shutdown VEN=0V 17 30 µA
Switching Characteristics
R
DS-UP-ON
R
DS- DN-ON
V
G-UVLO
Main MOSFET Rds(on) 0.18 0.35 Ω
Syn. MOSFET Rds(on) 0.11 0.2 Ω
Gate drive voltage UVLO V
BST-VSW
increasing 3.3 4 V
Soft-start
I
SS
SS pin source current VSS= 0.5V 6 8 9.8 µA
Current Limit
I
CL
Syn. MOSFET current limit threshold 1.9 A
ON/OFF Timer
t
ON
t
ON-MIN
t
OFF
ON timer pulse width VIN= 10V, RON= 100 kΩ 1.38 µs
V
= 30V, RON= 100 kΩ 0.47
IN
ON timer minimum pulse width 200 ns
OFF timer pulse width 260 ns
Enable Input
V
EN-HYS
V
EN
EN Pin input threshold VENrising 1.236 1.26 1.285 V
Enable threshold hysteresis VENfalling 90 mV
Regulation and Over-Voltage Comparator
V
V
FB
FB-OV
I
FB
In-regulation feedback voltage VSS≥ 0.8V
= −40˚C to + 125˚C
T
J
V
≥ 0.8V
SS
= 0˚C to + 125˚C
T
J
Feedback over-voltage threshold 0.894 0.920 0.940 V
0.784 0.8 0.816 V
0.788 0.812
5 100 nA
Thermal Shutdown
T
SD
Thermal shutdown temperature TJrising 165 ˚C
www.national.com 4
LM3100
Electrical Charateristics Specifications with standard type are for T
over the full Operating Junction Temperature (T
statistical correlation. Typical values represent the most likely parametric norm at T
purposes only. Unless otherwise stated the following conditions apply: V
) range. Minimum and Maximum limits are guaranteed through test, design, or
J
= 18V, V
IN
= 25˚C only; limits in boldface type apply
J
= 25˚C, and are provided for reference
J
= 3.3V. (Continued)
OUT
Symbol Parameter Conditions Min Typ Max Units
T
SD-HYS
Thermal shutdown temperature
TJfalling 20 ˚C
hysteresis
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 1.5kΩ resistor into each pin.
Note 3: θ
@
60˚C.
Note 4: V
measurements are performed in general accordance with Mil-Std 883B, Method 1012.1 and utilizes the copper heat sink technique. Copper Heat Sink
JC
provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.
CC
www.national.com5
Loading...