參數(shù)資料
型號: L4985D
元件分類: 基準電壓源/電流源
英文描述: Voltage-Mode SMPS Controller
中文描述: 電壓模式開關電源控制器
文件頁數(shù): 1/23頁
文件大?。?/td> 415K
代理商: L4985D
L4985
HIGH EFFICIENCY SWITCHING REGULATOR
PRODUCT PREVIEW
OPERATINGINPUT VOLTAGE:
FROM4.5V TO 21V
HIGHEFFICIENCY3ASTEPDOWNCONVERTER
3A @ 3.3V OUTPUT VOLTAGE FROM 4.5V
INPUT VOLTAGE
ADJUSTABLE OUTPUT VOLTAGE
FROM 1.28V
GATE
DRIVER
FOR
RECTIFICATION
100% MAXIMUMDUTY CYCLE
INTERNAL CURRENT LIMIT
SOFT START, RESET SIGNAL,
THERMAL SHUTDOWN
AUXILIARY
CONVERTER
OPEN DRAIN SWITCH DELIVERING 5W
@ V
IN
= 12V
1.7A PEAKCURRENT INTERNALLY
LIMITED(TYP)
POWER MANAGEMENT
SYNCHRONOUS
WITH
40V
DESCRIPTION
This high efficiency DC-DC converter is a mono-
lithic device developed to generate all the volt-
ages required in multioutputs DC-DC converters,
in particular when the supply voltage is a battery,
and isolation is not needed.
Designed to start to operate at an inputvoltage as
low as 4.5V up to 21V, the device takes the ad-
vantages offered by our proprietary BCD Mul-
tipower technology to deliver 3A to the load on
the stepdown section, and to manage 1.5A peak
current on the open drain section.
The packagesproposed are in plastic dual in line,
Powerdip 20 (16+2+2) for standard assembly,
and SO20Lfor SMD assembly.
This device is constitueed by two major sections:
one section is a stepdown regulator, and the
other one is a flexible regulator with open drain
output DMOS transistor, source grounded, for fly-
back/forward topologies for multioutputs, or step-
up topologywhen a single voltage higher than the
supply one is requested.
Step Down Converter Section
The stepdownsection, delivering to the load up to
3A current, at an output voltage adjustable from
1.28V up to 16V,works in voltage mode, fixed fre-
quency,with no limitation on the maxduty cycle.
This section has been designed to maximise the
efficiency minimising the conduction losses and
the quiescentcurrent.
An internal step-up converter using a small chip
inductor and a filter capacitor provides voltage
and energy the gate driver of the internal N-chan-
nel DMOS transistor of 0.1
typ of R
dson
, and the
driver of an external DMOS transistor that should
require no more than 30nC of gate charge, at
100KHz.
The gate driver pin can be leftopen if the use of a
Schottkydiode is preferred.
An internal pulse by pulse current limiting protects
the device it self and the load from overload and
short circuit conditions.
A reset block, monitoring the feedback voltage,
with an programmable reset delay time, gener-
ates a reset signalfor the microprocessor.
The reset output is an opendrain.
Moreover, the DIS1 pin, active low, will inhibit the
whole device, reducing to leakage only the cur-
rent consumptionfrom the battery.
Thisis advancedinformation on a new productnow in developmentor undergoing evaluation. Details are subjectto change without notice.
March 1995
ORDERING NUMBERS:
L4985 (Powerdip)
L4985D (SO20)
POWERDIP 16+2+2
SO20
MULTIPOWER BCD TECHNOLOGY
1/23
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