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PDF TD1484B Data sheet ( Hoja de datos )
| Número de pieza | TD1484B | |
| Descripción | 3A 23V Synchronous Rectified Step-Down Converter | |
| Fabricantes | Techcode | |
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Techcode®
DATASHEET
3A 23V Synchronous Rectified Step-Down Converter TD1484B
General Description
Features
The TD1484B is a monolithic synchronous buck regulator.
The device integrates two 90mΩ MOSFETs, and
provides 3A of continuous load current over a wide input
voltage of 4.75V to 23V. Current mode control
provides fast transient response and cycle-by-cycle current
limit.
An adjustable soft-start prevents inrush current at turn-on,
and in shutdown mode the supply current drops to 1µA.
The TD1484B regulates the output voltage in automatic
PSM/PWM mode operation, depending on the outputcurrent,
for high efficiency operation over light to full load current.
This device, available in an SOP8-PP package, provides
a very compact solution with minimal external components.
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•
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3A Output Current
Wide 4.75V to 23V Operating Input Range
Integrated 90mΩ Power MOSFET Switches
Output Adjustable from 0.923V to 20V
Up to 93% Efficiency
Pulse Save Mode(PSM)/PWM Mode Operation
Programmable Soft-Start
Stable with Low ESR CeramicOutputCapacitors
Fixed 340KHz Frequency
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Applications
• Distributed Power Systems
• Networking Systems
• FPGA, DSP, ASIC Power Supplies
• Green Electronics/ Appliances
• Notebook Computers
Package Types
October, 20, 2010.
Figure 1. Package Types of TD1484B
Techcode Semiconductor Limited
1
SOP8
www.techcodesemi.com
1 page  
Techcode®
DATASHEET
3A 23V Synchronous Rectified Step-Down Converter TD1484B
Electrical Characteristics
VIN = 12V, Ta = 25℃ unless otherwise specified.
Parameters
Shutdown Supply Current
Symbol
Supply Current
Feedback Voltage
VFB
Feedback Overvoltage Threshold
Error Amplifier Voltage Gain *
AEA
Error Amplifier Transconductance
GEA
High-Side Switch On Resistance * RDS(ON)1
Low-Side Switch On Resistance * RDS(ON)2
High-Side Switch Leakage
Current
Upper Switch Current Limit
Lower Switch Current Limit
COMP to Current Sense
Transconductance
GCS
Oscillation Frequency
Fosc1
Short Circuit Oscillation
Frequency
Fosc2
Maximum Duty Cycle
DMAX
Minimum On Time *
EN Shutdown Threshold Voltage
EN Shutdown Threshold Voltage
Hysteresis
EN Lockout Threshold Voltage
EN Lockout Hysterisis
Test Condition
VEN = 0V
VEN = 2.0V; VFB =
1.0V
4.75V ≤ VIN ≤ 23V
∆IC = ±10µA
VEN = 0V, VSW = 0V
Minimum Duty Cycle
From Drain to Source
VFB = 0V
VFB = 1.0V
VEN Rising
Min.
0.900
4.0
1.1
2.2
Typ. Max.
1 3.0
1.3 1.5
0.923 0.946
1.1
400
800
90
90
10
5.8
0.9
4.8
340
100
90
220
1.5 2.0
210
2.5 2.7
210
Unit
µA
mA
V
V
V/V
µA/V
mΩ
mΩ
µA
A
A
A/V
KHz
KHz
%
ns
V
mV
V
mV
October, 20, 2010.
Techcode Semiconductor Limited
5
www.techcodesemi.com
5 Page 
Techcode®
DATASHEET
3A 23V Synchronous Rectified Step-Down Converter TD1484B
their Manufacturers.
Part Number
B130
SK13
MBRS130
Voltage/Current
30V, 1A
30V, 1A
30V, 1A
Vendor
Diodes, Inc.
Diodes, Inc.
International Rectifier
Input Capacitor
The input current to the step-down converter is
discontinuous, therefore a capacitor is required to supply the
AC current to the step-down converter while maintaining the
DC input voltage. Use low ESR capacitors for the best
performance. Ceramic capacitors are preferred, but tantalum
or low-ESR electrolytic capacitors may also suffice. Choose
X5R or X7R dielectrics when using ceramic capacitors.
Since the input capacitor (C1) absorbs the input switching
current it requires an adequate ripple current rating. The
RMS current in the input capacitor can be estimated by:
The worst-case condition occurs at VIN = 2VOUT,where IC1 =
ILOAD/2. For simplification, choose the input capacitor whose
RMS current rating greater than half of the maximum load
current.
The input capacitor can be electrolytic, tantalum or ceramic.
When using electrolytic or tantalum capacitors, a small, high
quality ceramic capacitor, i.e. 0.1μF, should be placed as
close to the IC as possible. When using ceramic capacitors,
make sure that they have enough capacitance to provide
sufficient charge to prevent excessive voltage ripple at input.
The input voltage ripple for low ESR capacitors can be
estimated by:
Where C1 is the input capacitance value.
Output Capacitor
The output capacitor is required to maintain the DC output
voltage. Ceramic, tantalum, or low ESR electrolytic capacitors
are recommended. Low ESR capacitors are preferred to keep
the output voltage ripple low. The output voltage ripple can
be estimated by:
Where C2 is the output capacitance value and RESR is the
equivalent series resistance (ESR) value of the output
capacitor.
In the case of ceramic capacitors, the impedance at the
switching frequency is dominated by the capacitance. The
output voltage ripple is mainly caused by the capacitance. For
simplification, the output voltage ripple can be estimated by:
In the case of tantalum or electrolytic capacitors,the ESR
dominates the impedance at the switching frequency. For
simplification, the output ripple can be approximated to:
The characteristics of the output capacitor also affect the
stability of the regulation system. The TD1484B can be
optimized for a wide range of capacitance and ESR values.
Compensation Components
TD1484B employs current mode control for easy
compensation and fast transient response. The system
stability and transient response are controlled through the
COMP pin. COMP pin is the output of the internal
transconductance error amplifier. A series capacitor-resistor
combination sets a pole-zero combination to control the
characteristics of the control system.
The DC gain of the voltage feedback loop is given by:
Where AVEA is the error amplifier voltage gain;GCS is the
current sense transconductance and RLOAD is the load resistor
value.
The system has two poles of importance. One is due to the
compensation capacitor (C3) and the output resistor of the
error amplifier, and the other is due to the output capacitor
and the load resistor. These poles are located at:
October, 20, 2010.
Techcode Semiconductor Limited
11
www.techcodesemi.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet TD1484B.PDF ] | |
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