CATAT71991 Datasheet PDF - Chip Advanced Technology


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CATAT71991
Chip Advanced Technology

Part Number CATAT71991
Description 2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter
Page 15 Pages

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CATAT71991
2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter
Confidentiality Statement:
This Data Sheet (including any attachments) is for the sole use of the intended
recipient(s) and contains confidential, proprietary and privileged information. Any
unauthorized review, use, disclosure or distribution is prohibited. If you are not the
intended recipient, please immediately destroy all copies of the original message.



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2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter CAT71991
General Description
The CAT71991 is a high efficiency and up to 2A
output current step-down DC/DC converter series
that integrates a low on resistance NMOS on high
side. Including on the substrate with the listed
features is a high performance trans-conductance
error amplifier that provides tight voltage regulation
and accuracy under transient conditions. An under
voltage lockout circuit is built in to prevent start up
until the input voltage reaches to 4.75V. Other
features include an over current protection and
thermal shutdown. The CAT71991 is available in an
8 pins SOIC package.
Application
‹ Set-Top-Box, DVD, LCD Displays
‹ High Power LED Power Supply
‹ Distributed Power System
‹ Data comm. xDSL CPE
Pin Configuration
Features
‹ High Efficiency up to 92%
‹ 4.75V to 23V Wide Input Voltage Range
‹ Output Adjustable from 1.23 to 17V
‹ 2.0A Output Current
‹ 380kHz constant Frequency Operation
‹ Current Mode Control
‹ Over-temperature Protection
‹ Over Current Protection
‹ Under Voltage Lockout
‹ 25μA Shutdown Current
‹ CAT71991 with Soft Star Function
‹ SOP8 Package
‹ RoHS Compliant (100% Green available)
Ordering Information
Part Number
CAT71991CA
Package
SOP8
Ship
2500/ Tape & Reel
Typical Application
Efficiency Table
Efficiency VS Output Current at VIN=12V
100
90
80
70
60
50
40
0
5V
3.3V
1.8V
0.5 1 1.5
Output Current (A)
2
The CAT logo is a registered trademark of Chip Advanced Technology
2008 Chip Advanced Technology Inc. – All Right Reserved.
8/28/2008 Rev:0.85 2/16



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2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter CAT71991
Pin Description
Pin Symbol
Description
Connect SS to an external capacitor to control soft-start timing. If SS is open,
1 SS
internal soft-start about 160uS will be used.
High Side Gate Drive Boost Input. A capacitor must be connected from SW to BS.
2 BS This capacitor boosts the gate drive to the internal NMOS above VIN to fully turn it
ON.
3 VIN Power Supply Pin. The input voltage for the power supply is connected to Pin3.
4
SW
Power Switch Output. This is the output of a power MOSFET switch connected
directly to the input voltage.
5
GND
Ground Pin. This is the ground reference connection for all components in the
power supply.
Voltage Feedback Pin. This is the input to an error amplifier, which drives the PWM
6 FB controller. It’s necessary to connect this pin to the actual output of power supply to
set the DC output voltage.
Compensation Pin. This pin is used to compensate the regulation control loop.
7 COMP Connect a series RC network from COMP pin to GND pin to compensate the
regulation control loop.
8 EN Enable Pin. This input provides an electrical ON/OFF control of the power Supply.
Function Block Diagram
The CAT logo is a registered trademark of Chip Advanced Technology
2008 Chip Advanced Technology Inc. – All Right Reserved.
8/28/2008 Rev:0.85 3/16



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2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter CAT71991
Absolute Maximum Ratings
Input Supply Voltage…………..GND - 0.3V to +25V
SW Voltage…………………………...- 1 to VIN+0.3V
EN Voltage……….…………………..- 1 to VIN+0.3V
Other Pins………………………………- 0.3V to +6V
Boost Voltage ………..………………Vsw+6V
(<30V)
SW Peak Current………………………………….5.5 A
ESD Classification……………………………..Class 2
Junction Temperature Range…………………..150°C
Storage Temperature Range…………-65oC to 150°C
Lead Temperature (Soldering 10s)…………….260°C
Recommended Operating Conditions
Supply Voltage (VIN)……………………4.75V to 23V
Operating Temperature……………..–40°C to +85°C
Thermal Resistance: θJA
SOIC Package………………..….91
θJC
43 (°C/W)
*Note: The IC has a protection circuit against static electricity. Do not apply high static electricity or high voltage that exceeds the
performance of the protection circuit to the IC.
Electrical Characteristic
(Recommended Operating Conditions, Unless Otherwise Noted; VIN = 12V; TA = 25 oC)
Parameter
Test Conditions
Min Typ. Max Unit
Supply Voltage
Shutdown Supply Current
Regulated Feedback Voltage
Error Amplifier Transconductance
Current sense to COMP
Transconductance
Current Limit
SW Leakage Current
High Side On Resistance
Low Side On Resistance
Oscillation frequency
Short Circuit Oscillation
Frequency
Maximum Duty Cycle
Minimum Duty Cycle
Under Voltage Lockout Threshold
Under Voltage Lockout Threshold
Hysteresis
Thermal Shutdown Threshold
EN High Level
EN Low Level
EN Input Current
Soft Start
VEN = 0V
4.75VVIN23V
ICOMP = ±10μA
VEN = 0V, VSW = 0V
I
VFB=0V
VFB=1.0V
VFB=1.5V
VIN Rising
VEN = 0V
Pin is opened
4.75
1.19
3.9
2.6
1.1
1.23
830
2.2
4
0.25
10
380
190
90
4.1
200
160
1.8
160
23
1.26
0
4.3
0.9
2.5
V
μA
V
μA/V
A/V
A
μA
KHz
KHz
%
%
V
mV
V
V
μA
us
The CAT logo is a registered trademark of Chip Advanced Technology
2008 Chip Advanced Technology Inc. – All Right Reserved.
8/28/2008 Rev:0.85 4/16




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