LM3103 Synchronous 1-MHz 0.75-A Step-Down Voltage Regulator

1 Features

Input Voltage Range 4.5 V to 42 V
0.75 A Output Current
0.6V, ±2% Reference
Integrated Dual N-Channel Main and Synchronous MOSFETs
Low Component Count and Small Solution Size
Stable with Ceramic and Other Low ESR Capacitors
No Loop Compensation Required
High Efficiency at a Light Load by DCM Operation
Pre-bias Startup
Ultra-Fast Transient Response
Programmable Soft-Start
Programmable Switching Frequency up to 1 MHz
Valley Current Limit
Thermal Shutdown
Output Over-Voltage Protection
Precision Internal Reference for an Adjustable Output Voltage Down to 0.6 V
Thermally Enhanced HTSSOP-16 Package

2 Applications

5VDC, 12VDC, 24VDC, 12VAC, and 24VAC Systems
Embedded Systems
Industrial Control
Automotive Telematics and Body Electronics
Point of Load Regulators
Storage Systems
Broadband Infrastructure
Direct Conversion from 2,3,4 Cell Lithium Batteries Systems

3 Description

The LM3103 Synchronously Rectified Buck Converter features all required functions to implement a highly efficient and cost effective buck regulator. It is capable of supplying 0.75 A to loads with an output voltage as low as 0.6 V. Dual N-Channel synchronous MOSFET switches allow a low component count, thus reducing complexity and minimizing board size.

Different from most other COT regulators, the LM3103 does not rely on output capacitor ESR for stability, and is designed to work exceptionally well with ceramic and other very low ESR output capacitors. It requires no loop compensation, results in a fast load transient response and simple circuit implementation. The operating frequency remains nearly constant with line variations due to the inverse relationship between the input voltage and the on-time. The operating frequency can be externally programmed up to 1 MHz. Protection features include V_CC under-voltage lock-out, output over-voltage protection, thermal shutdown, and gate drive under-voltage lock-out. The LM3103 is available in the thermally enhanced HTSSOP-16 package.

Device Information (1)

PART NUMBER	PACKAGE	BODY SIZE (NOM)
LM3103	HTSSOP-16	5.00 mm × 4.40 mm

For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application Schematic

4 Revision History

Changes from F Revision (April 2013) to G Revision

Changed layout of National Data Sheet to TI formatGo

5 Pin Configuration and Functions

PWP Package

16-Pin HTSSOP

Top View

Pin Functions

Pin	Name	Description	Application Information
1, 2	VIN	Input supply voltage	Supply pin to the device. Nominal input range is 4.5 V to 42 V.
3, 4	SW	Switch Node	Internally connected to the source of the main MOSFET and the drain of the synchronous MOSFET. Connect to the output inductor.
5	BST	Connection for bootstrap capacitor	Connect a 33 nF capacitor from the SW pin to this pin. This capacitor is charged through an internal diode during the main MOSFET off-time.
6	AGND	Analog Ground	Ground for all internal circuitry other than the PGND pin.
7	SS	Soft-start	A 70 µA internal current source charges an external capacitor of larger than 22 nF to provide the soft-start function.
8	NC	No Connection	This pin should be left unconnected.
9, 10	GND	Ground	Must be connected to the AGND pin for normal operation. The GND and AGND pins are not internally connected.
11	FB	Feedback	Internally connected to the regulation and over-voltage comparators. The regulation setting is 0.6 V at this pin. Connect to feedback resistors.
12	EN	Enable pin	Internal pull-up. Connect to a voltage higher than 1.6 V to enable the device.
13	RON	On-time Control	An external resistor from the VIN pin to this pin sets the main MOSFET on-time.
14	VCC	Startup regulator Output	Nominally regulated to 6 V. Connect a capacitor of larger than 1 µF between the VCC and AGND pins for stable operation.
15, 16	PGND	Power Ground	Synchronous MOSFET source connection. Tie to a ground plane.
DAP	EP	Exposed Pad	Thermal connection pad. Connect to the ground plane.