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PDF TD2676 Data sheet ( Hoja de datos )
| Número de pieza | TD2676 | |
| Descripción | 2.5A 52KHz 32V PWM Buck DC/DC Converter | |
| Fabricantes | Techcode | |
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T echcode®
2.5A 52KHz 32V PWM Buck DC/DC Converter
DATASHEET
TD2676
General Description
Features
The TD2676 is a 52 KHz fixed frequency monolithic step
down switch mode regulator with a built in internal Power
MOSFET. It achieves 2.5A continuous output current
over a wide input supply range with excellent load and
line regulation.
The device includes a voltage reference, oscillation
circuit, error amplifier, internal PMOS and etc.
The PWM control circuit is able to adjust the duty ratio
linearly from 0 to 100%. An enable function, an over
current protection function and a short circuit protection
function are built inside. An internal compensation block
is built in to minimize external component count.
2.5A Constant Output Current
80mΩ RDSON Internal Power PMOSFET Switch
Up to 95% Efficiency
Fixed 52KHz Frequency
Wide 3.6V to 32V Input Voltage Range
Output Adjustable from 0.8V to 30V
Built in Frequency Compensation
Built in Thermal Shutdown Function
Built in Current Limit Function
SOP-8 Package is Available
The minimum dropout up to 0.3V
Applications
The TD2676 serves as ideal power supply units for
portable devices.
z
z
Portable DVD
LCD Monitor / TV
z Battery Charger
z ADSL Modem
z Telecom / Networking Equipment
Package Types
Figure 1. Package Types of TD2676
December, 23, 2009. Techcode Semiconductor Limited www.techcodesemi.com
1
1 page  
T echcode®
2.5A 52KHz 32V PWM Buck DC/DC Converter
Electrical Characteristics
DATASHEET
TD2676
Specifications with boldface type are for full operationg temperature range, the other type are for TJ=25OC.
Note1: Thermal resistance with copper area of approximately 3 in2.
Parameters
Symbol
Test Condition Min.
Typ.
Max. Unit
Input voltage
Shutdown Supply Current
VIN
ISTBY
VEN=0V
3.6
30
32 V
90 uA
Supply Current
ICC
VEN=2V, VFB=0.8V
3.6 4 mA
Feedback Voltage
Feedback Bias Current
Switch Current Limit
VFB VIN = 3.6V to 23V 0.78 0.8 0.82 V
IFB
VFB=0.8V
0.1 0.5 uA
ILIM 3.5 4.5 A
Oscillator Frequency
Frequency of Current
Limit or Short Circuit
Protection
FOSC
FOSC1
VFB=0V
47 52 58 KHz
42 KHz
EN Pin Threshold
VEN
0.7 1.2 1.7 V
EN Pin Input Leakage
Current
IH
IL
Internal PMOS RDSON
RDSON
Max. Duty Cycle
DMAX
Efficiency
η
Thermal Shutdown
TOTSD
VEN=2.5V
VEN=0.5V
VIN =12V, VFB=0V
VEN=12V, Iout=2A
VFB=0V, ISW=0.1A
VIN=12V ,Vout=5V
Iout=2A
‐0.1 ‐1 uA
‐3 ‐10 uA
80 mΩ
100 %
‐ 92 ‐ %
165 ºC
December, 23, 2009. Techcode Semiconductor Limited www.techcodesemi.com
5
5 Page 
T echcode®
2.5A 52KHz 32V PWM Buck DC/DC Converter
DATASHEET
TD2676
Function Description(Cont.)
Inductor
The inductor is required to supply constant current to the
output load while being driven by the switched input
voltage. A larger value inductor results in less ripple
current that in turn results in lower output ripple voltage.
However, the larger value inductor has a larger physical
size, higher series resistance, and/or lower saturation
current. Choose an inductor that does not saturate under
the worst-case load conditions. A good rule for
determining the inductance is to allow the peak-to-peak
ripple current in the inductor to be approximately 30% of
the maximum load current. Also, make sure that the peak
inductor current (the load current plus half the
peak-to-peak inductor ripple current) is below the TBDA
minimum current limit. The inductance value can be
calculated by the equation:
L = (VOUT) * (VIN-VOUT) / VIN * f * ∆I
Where VOUT is the output voltage, VIN is the input
voltage, f is the switching frequency, and ∆I is the
peak-to-peak inductor ripple current.
Input Capacitor
The input current to the step-down converter is
discontinuous, and so a capacitor is required to supply
the AC current to the step-down converter while
maintaining the DC input voltage. A low ESR capacitor is
required to keep the noise at the IC to a minimum.
Ceramic capacitors are preferred, but tantalum or
low-ESR electrolytic capacitors may also suffice.
The input capacitor value should be greater than 10μF.
The capacitor can be electrolytic, tantalum or ceramic.
However since it absorbs the input switching current it
requires an adequate ripple current rating. Its RMS
current rating should be greater than approximately
1/2 of the DC load current.
For insuring stable operation should be placed as close
to the IC as possible.Alternately a smaller high quality
ceramic 0.1μF capacitor may be placed closer to the IC
and a larger capacitor placed further away. If using this
technique, it is recommended that the larger capacitor be
a tantalum or electrolytic type. All ceramic capacitors
should be places close to the TD2676.
Output Capacitor
The output capacitor is required to maintain the DC
output voltage. Low ESR capacitors are preferred to
keep the output voltage ripple low. The characteristics of
the output capacitor also affect the stability of the
regulation control system. Ceramic, tantalum,or low ESR
electrolytic capacitors are recommended. In the case of
ceramic capacitors, the impedance at the switching
frequency is dominated by the capacitance,and so the
output voltage ripple is mostly independent of the ESR.
The output voltage ripple is estimated to be:
VRIPPLE ~= 1.4 * VIN * (fLC/fSW)^2
Where VRIPPLE is the output ripple voltage, VIN is the
input voltage, fLC is the resonant frequency of the LC
filter, fSW is the switching frequency. In the case of
tanatalum or low-ESR electrolytic capacitors, the ESR
dominates the impedance at the switching frequency,
and so the output ripple is calculated as:
VRIPPLE ~= ∆I * RESR
Where VRIPPLE is the output voltage ripple, ∆I is the
inductor ripple current, and RESR is the equivalent
series resistance of the output capacitors.
Output Rectifier Diode
The output rectifier diode supplies the current to the
inductor when the high-side switch is off.
To reduce losses due to the diode forward voltage and
recovery times, use a Schottky rectifier.
Table 1 provides the Schottky rectifier part numbers
based on the maximum input voltage and current rating.
December, 23, 2009. Techcode Semiconductor Limited www.techcodesemi.com
11
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| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet TD2676.PDF ] | |
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