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PDF LA8525 Data sheet ( Hoja de datos )
| Número de pieza | LA8525 | |
| Descripción | 2A/21V Step-Down DC-DC Converter | |
| Fabricantes | Linear Artwork | |
| Logotipo |  |
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General Description
LA8525/A
500KHz, 2A/21V Step-Down DC-DC Converter
Features
LA8525/A is a current mode, step-down DC-DC
converter that is designed to meet 2A output
current, and utilizes PWM control scheme that
switches with 500KHz fixed frequency.
The input voltage range of LA8525/A is from
4.5V to 21V, and available in adjustable output
voltage from 0.8V to VIN. The supply current is
only 1mA during operation and under 20uA in
shutdown.
This device provides an enable function that
can be controlled by external logic signal. It
also provides excellent regulation during line
or load transient. Other features of soft-start,
current limit, thermal shutdown protection,
and short circuit protection are also included.
To increase light-load conversion efficiency,
the Power-Saving Mode (PSM) feature is
automatically activated. This device can also
operate with a maximum duty cycle of 100%
for use in low drop-out conditions. The
package is available in standard SOP-8.
l 4.5V to 21V Input Voltage Range
l Continuous 2A Output Capability
l 0.8V Reference Voltage
l 100% Duty Cycle
l 20uA Low Shutdown Current
l 1mA Low Supply Current
l 500KHz Switching Frequency in PWM Mode
l Power-Saving Mode (PSM) at Light-Load
l Current Mode for Excellent Response
l Internal Soft-Start & Current Limit
l No External Compensation Required
l Support Low ESR Output Ceramic Capacitors
l Short Circuit & Thermal Shutdown Protection
l Standard SOP-8 Package
l Meet RoHS Standard
Applications
l Wireless / Broadband Communication
l LCD TV / Monitor
l Set-Top-Box
l Portable Device
Ordering Information
LA8525/A 1 2 3 4 ; (A: Bonding Code)
1 (Package Type) => J: SOP
2 (Number of Pins) => G: 8 pin
3 (Output Voltage) => Blank: Adjustable
4 (Special Feature) => Blank: N/A
Available Part Number
LA8525JG
LA8525AJG
Marking Information
NC GND SW SW
NC EN NC FB
LA8525JG
1234
LA8525AJG
1234
FB EN NC IN LA8525
NC IN SW GND LA8525A
1 2 (Date Code)
For date code rule, please contact our sales
representative directly.
3 4 (Internal Code)
LA8525(A)-B01
-1-
Dec. 26, 2010
www.linear-artwork.com
1 page  
LA8525/A
Absolute Maximum Ratings
Parameter
Rating
Input Voltage
23V
SW Pin Voltage Range
FB Pin Voltage Range
-0.5V ~ VIN+0.5V
-0.3V ~ 6V
EN Pin Voltage Range
Storage Temperature Range
-0.3V ~ VIN+0.3V
-65°C ~ 150°C
Junction Temperature
150°C
Lead Soldering Temperature (10 sec)
300°C
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for
prolonged time periods may affect device reliability. All voltages are with respect to ground.
Recommended Operating Conditions
Parameter
Rating
Input Voltage Range
4.5V ~ 21V
Ambient Temperature Range
-40oC ~ 85oC
Junction Temperature Range
-40oC ~ 125oC
These are conditions under which the device functions but the specifications might not be guaranteed. For
guaranteed specifications and test conditions, please see the Electrical Specifications.
Package Information
Parameter
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Package
SOP-8
Symbol
θJC
θJA
Rating
40 oC/W
105 oC/W
LA8525(A)-B01
-5-
Dec. 26, 2010
www.linear-artwork.com
5 Page 
LA8525/A
Delay Start-up
The following circuit uses the EN pin to provide a time delay between the input voltage is applied
and the output voltage comes up. As the instant of the input voltage rises, the charging of
capacitor CDELAY pulls the EN pin low, keeping the device off. Once the capacitor voltage rises above
the EN pin threshold voltage, the device will start to operate. The start-up delay time can be
calculated by the following formula:
VIN
RDELAY
IN
EN GND
CDELAY
VEN
VIN x (1 – e-T/(RxC)) > VEN
Where T is the start-up delay time, R is RDELAY, C is CDELAY, and the typical VEN is 1.3V.
This feature is useful in situations where the input power source is limited in the amount of current
it can deliver. It allows the input voltage to rise to a higher voltage before the device starts
operating.
Snubber Circuit
The simple RC snubber is used for voltage transient and ringing suppression. The high frequency
ringing and voltage overshooting at the SW pin is caused by fast switching transition and
resonating circuit parasitical elements in the power circuit. It maybe generates EMI and interferes
with circuit performance. Reserve a snubber circuit in the PC board is preferred to damp the
ringing due to the parasitical capacitors and inductors of layout. The following circuit is a simple RC
snubber:
SW
FB
GND
C SN UB
RSNUB
VOUT
Choose the value of RC network by the following procedure:
(1) Measure the voltage ringing frequency (fR) of the SW pin.
(2) Find a small capacitor and place it across the SW pin and the GND pin to damp the ringing
frequency by half.
LA8525(A)-B01
- 11 -
Dec. 26, 2010
www.linear-artwork.com
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LA8525.PDF ] | |
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