DAC2800D 데이터 시트보기 (PDF) - M.S. Kennedy Corporation

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DAC2800D

6W DUAL DC-DC CONVERTERS

M.S. Kennedy Corporation 

DAC2812D • DAC2815D

APPLICATION

INFORMATION

OUTPUT ADJUST / COMP

The output voltage of the DAC2800D may be adjusted from

90% to 110% of nominal value by the use of a 150K( potenti-

ometer as shown. Adjustment beyond this range is possible,

however certain characteristics of the converter such as but

not limited to input voltage range, efficiency, ripple and tem-

perature performance will change. Characterization by the

user is recommended in such applications.

4

1

10nF

2

150K

Adjust/comp (pin 4) may be driven by external circuitry

referenced to pin 2 (-output) if desired. Grounding pin 4 causes

voltage to increase (25% typically) while driving pin 4 above

1.3 V causes output voltage to decrease. Pin 4 may be driven

negative without damage, however the resultant increase in

converter output voltage should be considered. Pin 4 may be

driven through 10K( or more if connection of the comp function

is also required.

The comp function of pin 4 allows load transient response

to be tailored to suit specific application requirements. This

feature may be utilized by connecting a 10nF or less capacitor

between pins 4 and 1.

SHUTDOWN PLUS

Pin 5 is used for remote shutdown, output fault detection,

and/or setting the input voltage point at which the converter

will turn on as shown in the typical application diagram. No

connection to pin 5 is necessary for normal operation of the

converter. Pin 5 is referenced to pin 7 (-input).

Shutdown may be implemented by simply connecting pin 5

to an open collector logic output or switch rated at 2.5 mA, 25

Vdc or higher.

Input voltage turn on point is programmed with a single

resistor from pin 5 to 7. An input turn on/off hysteresis (typically

3.5% of Vin) will be observed. This should be considered when

making or verifying set point adjustment. The value of the

setpoint resistor may be determined by the following:

R = 210 * 10 3

ETO – 9.5

(+/– 10% accuracy at 25OC)

Set point temperature coefficient is typically + 400ppm/OC

Output fault monitoring is accomplished by observing pin 5

with a high impedance monitoring circuit. Pin 5 voltage drops

from over 10 V to below 1 V when a load fault causes the

converter's fault protection circuitry to activate. It will remain

low for at least 100 mS and return high. If the load fault is still

present pin 5 will return low and the cycle will repeat. A resistor

> 400K( from pin 5 to 7 provides pull down for pin 5 if there is

no input setpoint programming resistor already in place.

LOAD FAULT RESPONSE

The DAC2800D series of DC-DC converters share load

fault philosophies. Load fault conditions include short-circuit

and severe overload conditions. The DAC2800D converter

series responds to load faults by turning off all power conver-

sion circuits for 250 mS and then attempting to restart for 10

mS (typical). The net "on" duty factor during a fault is very low

resulting in low converter dissipation and immunity from

overheating at 125°C. Current beyond rated can flow into the

load at startup time. This allows the converter to bring up

capacitive and other difficult load types more reliably than

competing converters.

Vo

O

Io

O

NORMAL

TIME

LOAD FAULT

NORMAL

6

Rev. B 12/03

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