LM20145MHE/NOPB National Semiconductor, LM20145MHE/NOPB Datasheet

IC REG SYNC BUCK 5A ADJ 16-TSSOP

LM20145MHE/NOPB

Manufacturer Part Number
LM20145MHE/NOPB
Description
IC REG SYNC BUCK 5A ADJ 16-TSSOP
Manufacturer
National Semiconductor
Series
PowerWise®r
Type
Step-Down (Buck)r
Datasheet

Specifications of LM20145MHE/NOPB

Internal Switch(s)
Yes
Synchronous Rectifier
Yes
Number Of Outputs
1
Voltage - Output
0.8 ~ 5 V
Current - Output
5A
Frequency - Switching
250kHz ~ 750kHz
Voltage - Input
2.95 ~ 5.5 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP
Power - Output
2.6W
For Use With
LM20145EVAL - BOARD EVAL 5A POWERWISE LM20145
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Other names
LM20145MHE

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
LM20145MHE/NOPB
Manufacturer:
NS
Quantity:
428
© 2008 National Semiconductor Corporation
LM20145
5A, PowerWise
Regulator
General Description
The LM20145 is a full featured adjustable frequency syn-
chronous buck regulator capable of delivering up to 5A of
continuous output current. The current mode control loop can
be compensated to be stable with virtually any type of output
capacitor. For most cases, compensating the device only re-
quires two external components, providing maximum flexibil-
ity and ease of use. The device is optimized to work over the
input voltage range of 2.95V to 5.5V making it suited for a wide
variety of low voltage systems.
The device features internal over voltage protection (OVP)
and over current protection (OCP) circuits for increased sys-
tem reliability. A precision enable pin and integrated UVLO
allows the turn-on of the device to be tightly controlled and
sequenced. Start-up inrush currents are limited by both an
internally fixed and externally adjustable Soft-Start circuit.
Fault detection and supply sequencing is possible with the
integrated power good circuit.
The LM20145 is designed to work well in multi-rail power
supply architectures. The output voltage of the device can be
configured to track a higher voltage rail using the SS/TRK pin.
If the output of the LM20145 is pre-biased at startup it will not
sink current to pull the output low until the internal soft-start
ramp exceeds the voltage at the feedback pin.
The frequency of this device can be adjusted from 250 kHz to
750 kHz by connecting an external resistor from the RT pin to
ground.
The LM20145 is offered in a 16-pin eTSSOP package with an
exposed pad that can be soldered to the PCB, eliminating the
need for bulky heatsinks.
Typical Application Circuit
PowerWise
®
is a registered trademark of National Semiconductor Corporation.
®
Adjustable Frequency Synchronous Buck
300307
Features
Applications
Input voltage range 2.95V to 5.5V
Accurate current limit minimizes inductor size
97% peak efficiency
Adjustable switching frequency (250 kHz to 750 kHz)
32 mΩ integrated FET switches
Starts up into pre-biased loads
Output voltage tracking
Peak current mode control
Adjustable output voltage down to 0.8V
Adjustable Soft-Start with external capacitor
Precision enable pin with hysteresis
Integrated OVP, UVLO, power good and thermal
shutdown
eTSSOP-16 exposed pad package
Simple to design, high efficiency point of load regulation
from a 5V or 3.3V bus
High Performance DSPs, FPGAs, ASICs and
microprocessors
Broadband, Networking and Optical Communications
Infrastructure
January 16, 2008
30030701
www.national.com

Related parts for LM20145MHE/NOPB

LM20145MHE/NOPB Summary of contents

Page 1

... The LM20145 is offered in a 16-pin eTSSOP package with an exposed pad that can be soldered to the PCB, eliminating the need for bulky heatsinks. Typical Application Circuit ® PowerWise is a registered trademark of National Semiconductor Corporation. © 2008 National Semiconductor Corporation Adjustable Frequency Synchronous Buck Features ■ Input voltage range 2.95V to 5.5V ■ ...

Page 2

Connection Diagram Ordering Information Order Number Package Type LM20145MH eTSSOP-16 LM20145MHE LM20145MHX Pin Descriptions Pin # Name 1 SS/TRK Soft-Start or Tracking control input. An internal 5 µA current source charges an external capacitor to set the Soft-Start ramp rate. ...

Page 3

... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Voltages from the indicated pins to GND AVIN, PVIN, EN, PGOOD, SS/TRK, COMP, FB, RT Storage Temperature Junction Temperature Electrical Characteristics Limits in standard type are for T = 25° ...

Page 4

Symbol Parameter Enable V EN Pin turn-on Threshold IH_EN V EN Pin Hysteresis EN_HYS Thermal Shutdown T Thermal Shutdown SD T Thermal Shutdown Hysteresis SD_HYS Thermal Resistance θ Junction to Ambient JA Note 1: Absolute Maximum Ratings indicate limits beyond ...

Page 5

Error Amplifier Gain vs. Frequency 30030736 Load Regulation 30030738 Switching Frequency vs. Temperature 30030739 Line Regulation Feedback Pin Voltage vs. Temperature Switching Frequency vs 30030737 30030751 T 30030750 www.national.com ...

Page 6

Quiescent Current vs. V Enable Threshold vs. Temperature Peak Current Limit vs. Temperature www.national.com (Not Switching) IN 30030740 30030728 30030742 6 Shutdown Current vs. Temperature 30030741 UVLO Threshold vs. Temperature 30030745 Peak Current Limit vs. V OUT 30030754 ...

Page 7

Peak Current Limit vs 30030755 Line Transient Response 30030743 Start-Up (Tracking) 30030733 Load Transient Response Start-Up (Soft-Start) Power Down 7 30030734 30030744 30030732 www.national.com ...

Page 8

Short Circuit Input Current vs. V www.national.com P IN 30030756 8 vs. I GOOD PGOOD 30030727 ...

Page 9

Block Diagram 9 30030703 www.national.com ...

Page 10

Operation Description GENERAL The LM20145 switching regulator features all of the functions necessary to implement an efficient low voltage buck regula- tor using a minimum number of external components. This easy to use regulator features two integrated switches and is ...

Page 11

When activated, typically at 160°C, the LM20145 tri-states the power FETs and resets soft start. After the junction cools to approximately 150°C, the part starts up using the normal start up routine. This feature is provided to ...

Page 12

Design Guide This section walks the designer through the steps necessary to select the external components to build a fully functional power supply. As with any DC-DC converter numerous trade- offs are possible to optimize the design for efficiency, size, ...

Page 13

Where, C (F) is the minimum required output capacitance, OUT L (H) is the value of the inductor, V DROOP voltage drop ignoring loop bandwidth considerations, ΔI (A) is the load step change, R STEP ESR capacitor ESR, V (V) ...

Page 14

FIGURE 4. LM20145 Loop Compensation The power stage transfer function is dictated by the modula- tor, output LC filter, and load; while the feedback transfer function is set by the feedback resistor ratio, error amp gain, and external compensation network. ...

Page 15

If different start up times are needed the equation shown be- low can be used to calculate the start up time. As shown above, the start up time is influenced by the value of the Soft-Start capacitor C (F) and ...

Page 16

The second most common power on behavior is known as a ratiometric start up. This start up is preferred in applications where both supplies need the final value at the same time. Similar to the Soft-Start function, ...

Page 17

FIGURE 10. Schematic of LM20145 Highlighting Layout Sensitive Nodes 17 30030722 www.national.com ...

Page 18

... C1 as outline in the design guide. C1 30030760 = 5A) OUTMAX Manufacturer Qty National Semiconductor 1 Murata 1 Sanyo 1 Vishay 1 Vishay-Dale 1 Murata 1 Murata 1 Vishay-Dale 1 Vishay-Vitramon 1 Vishay-Dale 1 Vishay-Vitramon 1 Vishay-Dale 1 Vishay-Dale 1 Vishay-Dale 1 = 5A) OUTMAX Manufacturer Qty National Semiconductor 1 Murata 1 Sanyo 1 Vishay 1 Vishay-Dale 1 Murata 1 Murata 1 Vishay-Dale 1 Vishay-Vitramon 1 Vishay-Dale 1 Vishay-Vitramon 1 Vishay-Dale 1 ...

Page 19

Designator Description 4.99 kΩ, 0603 R FB1 10 kΩ, 0603 R FB2 Part Number Manufacturer CRCW06034991F-e3 Vishay-Dale CRCW06031002F-e3 Vishay-Dale 19 Qty 1 1 www.national.com ...

Page 20

Physical Dimensions www.national.com inches (millimeters) unless otherwise noted 16-Lead eTSSOP Package NS Package Number MXA16A 20 ...

Page 21

Notes 21 www.national.com ...

Page 22

... For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock Conditioners www.national.com/timing Data Converters www.national.com/adc Displays www.national.com/displays Ethernet www.national.com/ethernet Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www ...

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