Texas Instruments LM22670 Inverting Output Regulator LM22670INVEVAL/NOPB LM22670INVEVAL/NOPB Datenbogen
Produktcode
LM22670INVEVAL/NOPB
User's Guide
SNVA363E – September 2008 – Revised April 2013
AN-1888 LM22670 Evaluation Board Inverting Topology
1
Introduction
The LM22670 inverting evaluation board is designed to demonstrate the capabilities of the LM22670
switching regulator in a polarity-inverting topology. The LM22670 inverting evaluation board schematic
shown in
switching regulator in a polarity-inverting topology. The LM22670 inverting evaluation board schematic
shown in
is configured to provide an output of minus 5 V (-5 V) up to 1.5A load current with an
input voltage range of 6 V to 35 V. The typical operating frequency is 500 kHz.
The evaluation board is designed to operate at ambient temperatures up to 50°C. Typical evaluation board
performance and characteristics curves are shown in
performance and characteristics curves are shown in
through
shows the PCB
layout.
To aid in the design and evaluation of DC/DC polarity-inverting converter solutions based on the LM22670
switching regulator, the evaluation board can be re-configured for different output voltages.
switching regulator, the evaluation board can be re-configured for different output voltages.
The evaluation board is designed to highlight applications with a small solution size. This implies that there
will be a trade-off between size and the area of heat dissipation available. If this evaluation board is
operated continuously at a full 1.5A load, it will get hot. For more negative output voltages than the pre-
adjusted -5 V, the total output power as well as the total power conversion losses will increase.
will be a trade-off between size and the area of heat dissipation available. If this evaluation board is
operated continuously at a full 1.5A load, it will get hot. For more negative output voltages than the pre-
adjusted -5 V, the total output power as well as the total power conversion losses will increase.
Test points are provided to enable easy connection and monitoring of critical signals.
For more information about device function and electrical characteristics, see the LM22670/LM22670Q
42V, 3A SIMPLE SWITCHER®, Step-Down Voltage Regulator with Features Data Sheet (
42V, 3A SIMPLE SWITCHER®, Step-Down Voltage Regulator with Features Data Sheet (
). The
evaluation board can be reconfigured for a different load current and output voltage. For design limitations,
see
see
.
The performance of the evaluation board is as follows:
•
Input Range: 6 V to 35 V, 12 V nominal
•
Output Voltage: -5 V
•
Output Current Range: 0A to 1.5A
•
Frequency of Operation: 500 kHz
•
Board Size: 1.5 X 1.65 inches
•
Package: PSOP-8
2
Evaluation Board Startup
Before applying power to the LM22670 polarity-inverting evaluation board, all external connections should
be verified. The external power supply input must be turned off and connected with proper polarity to the
V
be verified. The external power supply input must be turned off and connected with proper polarity to the
V
IN
and GND posts. A load resistor or electronic load should be connected between the V
OUT
and GND
posts as desired. Both the V
IN
and V
OUT
connections should use the closest GND posts respective to V
IN
or
V
OUT
. The output voltage can be monitored with a multi-meter or oscilloscope at the V
OUT
post. Once all
connections to the evaluation board have been verified, input power can be applied. A load resistor or
electronic load does not need to be connected during startup. If the EN test point is left floating, the output
voltage will ramp up when an input voltage is applied. Make sure that the external power supply (input
voltage power source) is capable of providing enough current so that the adjusted output voltage can be
obtained. Keep in mind that the startup current will be greater than the steady state current.
electronic load does not need to be connected during startup. If the EN test point is left floating, the output
voltage will ramp up when an input voltage is applied. Make sure that the external power supply (input
voltage power source) is capable of providing enough current so that the adjusted output voltage can be
obtained. Keep in mind that the startup current will be greater than the steady state current.
SIMPLE SWITCHER is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
All other trademarks are the property of their respective owners.
1
SNVA363E – September 2008 – Revised April 2013
AN-1888 LM22670 Evaluation Board Inverting Topology
Copyright © 2008–2013, Texas Instruments Incorporated