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PDF RT8287A Data sheet ( Hoja de datos )
| Número de pieza | RT8287A | |
| Descripción | 500kHz Synchronous Step-Down Converter | |
| Fabricantes | Richtek | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de RT8287A (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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®
RT8287A
4A, 21V 500kHz Synchronous Step-Down Converter
General Description
The RT8287A is a synchronous step-down regulator with
an internal power MOSFET. It achieves 4A of 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
limiting and thermal shutdown. An adjustable soft-start
reduces the stress on the input source at startup.
The RT8287A requires a minimal number of readily
available external components, providing a compact
solution.
Features
z 4A Output Current
z Adjustable Soft-Start
z 120mΩ/40mΩ Internal Power MOSFET Switch
z Internal Compensation Minimizes External Parts
Count
z Fixed 500kHz Frequency
z Thermal Shutdown Protection
z Cycle-by-Cycle Over Current Protection
z Wide 4.5V to 21V Operating Input Range
z Adjustable Output from 0.808V to 15V
z Small 14-Lead WDFN Package
z RoHS Compliant and Halogen Free
Ordering Information
RT8287A
Package Type
QW : WDFN-14L 4x3 (W-Type)
Lead Plating System
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
01 : Product Code
01 YM
DNN
YMDNN : Date Code
Applications
z Distributive Power Systems
z Battery Charger
z DSL Modems
z Pre-Regulator for Linear Regulators
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Pin Configurations
(TOP VIEW)
VIN 1
SW 2
SW 3
SW 4
SW 5
BOOT 6
EN 7
GND
15
14 AGND
13 GND
12 GND
11 VCC
10 SS
9 PGOOD
8 FB
WDFN-14L 4x3
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8287A-03 June 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
datasheet pdf - http://www.DataSheet4U.net/
1 page  
RT8287A
Parameter
Power Good Rising Threshold
Power Good Falling Threshold
Power Good Delay
Power Good Sink Current
Capability
Power Good Leakage Current
Under Voltage Lockout
Threshold
Under Voltage Lockout
Threshold Hysteresis
VCC Regulator
VCC Load Regulation
Soft-Start Period
Thermal Shutdown
Thermal Shutdown Hysteresis
Symbol
VUVLO
ΔVUVLO
tSS
TSD
ΔTSD
Test Conditions
Sink 4mA
VIN Rising
ICC = 5mA
CSS = 47nF
Min Typ Max Unit
-- 90 -- %
-- 70 -- %
-- 20 --
μs
-- -- 0.4 V
-- 10 -- nA
3.8 4 4.2 V
-- 400 -- mV
-- 5 -- V
-- 5 -- %
-- 4.7 -- ms
-- 150 -- °C
-- 30 -- °C
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
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Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8287A-03 June 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
datasheet pdf - http://www.DataSheet4U.net/
5 Page 
RT8287A
be greater than the short circuit peak current limit. Please
see Table 2 for the inductor selection reference and it is
highly recommended to keep inductor value as close as
possible to the recommended inductor values for each
VOUT as shown in Table 1.
Table 2. Suggested Inductors for Typical
Application Circuit
Component Supplier Series Dimensions (mm)
TDK
VLF10045 10 x 9.7 x 4.5
TDK
SLF12565 12.5 x 12.5 x 6.5
TAIYO YUDEN NR8040
8x8x4
Input and Output Capacitors Selection
The input capacitance, CIN, is needed to filter the
trapezoidal current at the source of the high side MOSFET.
To prevent large ripple current, a low ESR input capacitor
sized for the maximum RMS current should be used. The
RMS current is given by :
IRMS
=
IOUT(MAX)
VOUT
VIN
VIN −1
VOUT
This formula has a maximum at VIN = 2VOUT, where IRMS =
IOUT / 2. This simple worst case condition is commonly
used for design because even significant deviations do
not offer much relief.
Choose a capacitor rated at a higher temperature than
required. Several capacitors may also be paralleled to
meet size or height requirements in the design.
For the input capacitor, one 22μF low ESR ceramic
capacitors are recommended. For the recommended
capacitor, please refer to Table 3 for more detail.
Location
CIN
CIN
COUT
COUT
COUT
COUT
Table 3. Suggested Capacitors for CIN and COUT
Component Supplier
Part No.
Capacitance (μF)
MURATA
GRM32ER71C226M
22
TDK
C3225X5R1C226M
22
MURATA
GRM31CR60J476M
47
TDK
C3225X5R0J476M
47
MURATA
G RM32ER 71C 226Mhttp://www.DataSheet4U.net/
22
TDK
C3225X5R1C226M
22
Case Size
1210
1210
1206
1210
1210
1210
The selection of COUT is determined by the required ESR
to minimize voltage ripple.
Moreover, the amount of bulk capacitance is also a key
for COUT selection to ensure that the control loop is stable.
Loop stability can be checked by viewing the load transient
response.
The output ripple, ΔVOUT, is determined by :
ΔVOUT
≤
ΔIL
⎡⎢⎣ESR +
1
8fCOUT
⎤
⎥⎦
Higher values, lower cost ceramic capacitors are now
becoming available in smaller case sizes. Their high ripple
current, high voltage rating and low ESR make them ideal
for switching regulator applications. However, care must
be taken when these capacitors are used at input and
output. When a ceramic capacitor is used at the input
and the power is supplied by a wall adapter through long
wires, a load step at the output can induce ringing at the
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8287A-03 June 2012
input, VIN. At best, this ringing can couple to the output
and be mistaken as loop instability. At worst, a sudden
inrush of current through the long wires can potentially
cause a voltage spike at VIN large enough to damage the
part.
Thermal Shutdown
Thermal shutdown is implemented to prevent the chip from
operating at excessively high temperatures. When the
junction temperature is higher than 150°C, the whole chip
is shutdown. The chip is automatically re-enable when
the junction temperature cools down by approximately
30 degrees.
EMI Consideration
Since parasitic inductance and capacitance effects in PCB
circuitry would cause a spike voltage on SW pin when
high side MOSFET is turned-on/off, this spike voltage on
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
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11 Page | ||
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| PDF Descargar | [ Datasheet RT8287A.PDF ] | |
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