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CATAT71991 데이터시트 PDF




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부품번호 CATAT71991 기능
기능 2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter
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CATAT71991 데이터시트, 핀배열, 회로
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.




CATAT71991 pdf, 반도체, 판매, 대치품
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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CATAT71991 전자부품, 판매, 대치품
2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter CAT71991
Function Description
The CAT71991 is a fixed switching frequency
current mode PWM step-down converter. It
regulates input voltages from 4.75V to 23V
down to an output voltage as low as 1.23V, and
is able to supply up to 2A of load current.
Oscillator Frequency
Slope compensated current mode PWM control
provides stable switching and cycle-by-cycle
current limit for superior load and line response. It
also provides protection of the internal main
switch and synchronous rectifier. The CAT71991
switches at a fixed frequency (380 KHz) and
regulates the output voltage. During each cycle
the PWM comparator modulates the power
transferred to the load by changing the inductor
peak current based on the feedback error voltage.
During normal operation, the main switch is turned
on for a certain time to ramp the inductor current
at each rising edge of the internal oscillator, and
switched off when the peak inductor current is
above the error voltage. When the main switch
is off, the low side MOS will be turned on
immediately and stay on until either the next cycle
starts.
Short Circuit Protection
The CAT71991 has short circuit protection. When
the output is shorted to ground, the oscillator
frequency is reduced to prevent the inductor
current from increasing beyond the NMOS
current limit. The NMOS current limit is also
reduced to lower the short circuit current. The
frequency and current limit will return to the
normal values once the short circuit condition is
removed and the feedback voltage reaches 1.23V.
Maximum Load current
The CAT71991 can operate down to 4.75V input
voltage; however the maximum load current
decreases at lower input due to large I*R voltage
drop on the main switch and low side switch. The
slope compensation signal reduces the peak
inductor current as a function of the duty cycle to
prevent sub-harmonic oscillations at duty cycles
greater than 50%.
Enable
The EN pin provides electrical on/off control of the
The CAT logo is a registered trademark of Chip Advanced Technology
2008 Chip Advanced Technology Inc. – All Right Reserved.
regulator. Once the EN pin voltage exceeds the
threshold voltage, the regulator starts operation and
the internal slow start begins to ramp. If the EN pin
voltage is pulled below the threshold, the regulator
stops switching and the internal slow start resets.
Connecting the pin to ground or to any voltage less
than 0.9V will disable the regulator and activate the
shutdown mode.
Under Voltage Lockout
The CAT71991 incorporates an under voltage
lockout circuit to keep the device disable when VIN
is below the UVLO start threshold. During power up,
internal circuit are held inactive until VIN exceeds
the UVLO start threshold voltage. Once the UVLO
start threshold voltage is reached, device start-up
begins. The device operates until VIN fall below the
UVLO stop threshold voltage. The typical hysteretic
in the UVLO comparator is 200mV.
Soft Start
CAT71991 built in the soft start function to reduce
input inrush current while turn on. If let this pin open
it will provide about 160us timing such that the duty
from small to specific duty during turn on period.
Thus this function can lower the current stress on
input power, MOSFET, and freewheeling diode.
Connect a capacitor on this pin to program the soft
start time. It is defined as
tss=τ*Css ----- To be defined from RD.
Boost Capacitor
Connect a 10nF low ESR ceramic capacitor
between the BS pin and SW pin. This capacitor
provides the gate drive voltage for the high side
MOSFET.
Thermal Shutdown
The CAT71991 protects itself from overheating with
an internal thermal shutdown circuit. If the junction
temperature exceeds the thermal shutdown
threshold, the voltage reference is grounded and
high side MOSFET is turned off.
Compensation
The system stability is controlled through COMP pin.
It will present a general design procedure to help
insure a stable and operational circuit. The design
in this data sheet is optimized for particular
requirements. If different conversions are requires,
some of the components may need to be changed
8/28/2008 Rev:0.85 7/16

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부품번호상세설명 및 기능제조사
CATAT71991

2.0A 380KHz 23V High Efficiency Step-Down DC/DC Converter

Chip Advanced Technology
Chip Advanced Technology

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