DHC2803SK データシートの表示（PDF） - M.S. Kennedy
部品番号
コンポーネント説明
メーカー
DHC2803SK Datasheet PDF : 6 Pages
| |||
APPLICATION
INFORMATION
DHC2800S SERIES
OUTPUT ADJUST / COMP
The output voltage of the DHC2800S may be adjusted
from 90% to 110% of nominal value by the use of a 50KΩ
potentiometer 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
temperature performance will change. Characterization by
the user is recommended in such applications.
3
1
10nF
2
50K
Adjust/comp (pin 3) may be driven by external circuitry
referenced to pin 2 (-output) if desired. Grounding pin 3 causes
voltage to increase (25% typically) while driving pin 3 above
1.3 V causes output voltage to decrease. Pin 3 may be driven
through 10KΩ or more if connection of the comp function is
also required.
The comp function of pin 3 allows capacitive loads as large
as 1000 µF to be accommodated on the DHC2805S without
loss of stability. This feature may be utilized by connecting a
10 nF capacitor between pins 3 and 1. This is generally
recommended when low ESR load capacitances of 100 µF or
greater are used.
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 the –input (pin 7).
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 • 103 (±10% accuracy at 25°C)
ETO – 9.5
Set point temperature coefficient is typically +400ppm/°C.
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
converters 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
> 400 KΩ 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 DHC2800S series of dc-dc converters share load fault
philosophies. Load fault conditions include short-circuit and
severe overload conditions. The DHC2800 converter series
responds to load faults by turning off all power conversion
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
5
Rev. A 3/01
Share Link: 