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PDF PT1203 Data sheet ( Hoja de datos )
| Número de pieza | PT1203 | |
| Descripción | Synchronous Step-Down Converter | |
| Fabricantes | Powtech | |
| Logotipo |  |
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PT1203
2A, 18V, 350KHz
Synchronous Step-Down Converter
GENERAL DESCRIPTION
FEATURES
The PT1203 is a monolithic pulse-width-modulated
(PWM) synchronous step-down switch mode regulator
with two internal power MOSFETs. It achieves 2A
continuous output current over a wide input supply
range with excellent load and line regulation. Current
mode operation provides fast transient response and
eases loop stabilization. Fault condition protection
includes cycle-by-cycle current limit and thermal
shutdown.
The PT1203 requires a minimum number of external
components, available in SOP-8 and ESOP-8 package.
z 2A Output Current
z 0.13Ω Internal Power MOSFET Switch
z Stable with Low ESR Output Ceramic Capacitors
z Up to 93% Efficiency
z Fixed 350KHz Frequency
z Thermal Shutdown
z Cycle-by-Cycle Over Current Protection
z Wide 4.75V to 18V Operating Input Range
z Output Adjustable from 0.923V to 15V
z Available in 8-Pin SOP8 and ESOP8 Packages
APPLICATION
z PC Monitors
z LCD TV
z Distributed Power Systems
z Network Systems
z FPGA, DSP, ASIC Power Supplies
z Notebook Computers
ORDERING INFORMATION
PACKAGE
SOP-8
TEMPERATURE
RANGE
-40℃ to 85℃
ORDERING PART
NUMBER
PT1203ESOH
ESOP-8
-40℃ to 85℃
PT1203EESH
Note:
xxxxxX
Assembly Factory Code
Lot Number
TRANSPORT
MEDIA
Tape and Reel
2500 units
Tape and Reel
2500 units
MARKING
PT1203
xxxxxX
PT1203
xxxxxX
TYPICAL APPLICATION CIRCUIT
Figure1 ——PT1203 Typical application circuit
China Resources Powtech (Shanghai) Limited
PT1203_DS Rev EN1.0
WWW.CRPOWTECH.COM
Page1
1 page  
PT1203
2A, 18V, 350KHz
Synchronous Step-Down Converter
OPERATION DESCRIPTION
The PT1203 is a synchronous rectified current mode
step-down regulator. It regulates input voltage from
4.75V to 18V down to a voltage as low as 0.923V, and
supplies up to 2A of load current.
On the rising edge of internal oscillator, the Low-Side
MOSFET will be turned off and the High-Side
MOSFET will be turned on if the PWM comparator
output is low. The output voltage is measured at FB pin
through a resistive voltage divider and amplified
through the internal error amplifier, the voltage at the
COMP pin is compared with the switch current. As the
switch current ramp up, the PWM comparator will
output high, the High-Side MOSFET will be turned off
and the Low-Side MOSFET will be turned on until the
next rising edge of the internal oscillator.
When the output voltage exceeds 20% of the nominal
regulated voltage, the Over-Voltage comparator will be
tripped and turn off the High-Side MOSFET by
discharging the SS pin to GND.
When the FB voltage is less than 0.4V, the frequency of
the internal oscillator will be set to 90KHz to decease
the short circuit current.
APPLICATION INFORMATION
Setting the Output Voltage
The output voltage is set using a resistive voltage
divider from the output to FB pin. The voltage
divider divides the output voltage down to the
feedback voltage by the ratio:
VFB
= VOUT
R2
R1 + R2
,
where
the
VFB
is the
feedback voltage and VOUT is the output voltage.
Thus the output voltage is :
VOUT
=
0.923 *
R1 + R2
R2
.
The typical value of R2 is 10kΩ.
VOUT is the output voltage, VIN is the input
voltage, f SW is the switching frequency, and ΔI L
is the peak-to-peak inductor ripple current. Choose
an inductor that will not saturate under the maximum
inductor peak current. The peak inductor current can
be calculated by:
I LP
=
I LOAD
+
VOUT
2 * f sw * L
*
⎜⎜⎝⎛1
−
VOUT
VIN
⎟⎟⎠⎞
,
where
I LOAD is the load current.
Inductor Selection
The inductor is required to supply constant current to
the output load while being driven by the switched
input voltage. A larger value inductor will result in
less ripple current that will result in lower output
ripple voltage. A good rule for choosing the inductor
is to allow the peak-to-peak ripple current in the
inductor to be approximately 30% of the maximum
switch current limit. The inductance value can be
calculated by: L =
VOUT
f SW * ΔI L
*
⎜⎜⎝⎛1
−
VOUT
VIN
⎟⎟⎠⎞ ,
where
Input Capacitor Selection
The input current to the converter is discontinuous,
therefore a capacitor is required to supply the AC
current to the converter while maintaining the DC
input voltage. Use the low ESR capacitors for the
best performance. Ceramic capacitors are preferred,
but tantalum or low-ESR electrolytic capacitors may
also suffice.
Since the input capacitor absorbs the input switching
current it requires an adequate ripple current rating.
The RMS current in the input capacitor can be
estimated by:
China Resources Powtech (Shanghai) Limited
PT1203_DS Rev EN1.0
WWW.CRPOWTECH.COM
Page5
5 Page 
PACKAGE INFORMATION
PT1203
2A, 18V, 350KHz
Synchronous Step-Down Converter
SOP8
SYMBOL
A
A1
A2
b
c
D
E
E1
e
L
θ
DIMENSIONS IN MILLIMETERS
MIN
1.350
MAX
1.750
0.100
0.250
1.350
1.550
0.330
0.510
0.170
0.250
4.700
5.100
3.800
4.000
5.800
6.200
1.270(BSC)
0.400
1.270
0° 8°
DIMENSIONS IN INCH
MIN
0.053
MAX
0.069
0.004
0.010
0.053
0.061
0.013
0.020
0.006
0.010
0.185
0.200
0.150
0.157
0.228
0.244
0.050(BSC)
0.016
0.050
0° 8°
China Resources Powtech (Shanghai) Limited
PT1203_DS Rev EN1.0
WWW.CRPOWTECH.COM
Page11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet PT1203.PDF ] | |
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