參數(shù)資料
型號(hào): LEN-1/28-D12M
廠商: CD TECHNOLOGIES INC
元件分類: 電源模塊
英文描述: 1-OUTPUT 0.25 W DC-DC REG PWR SUPPLY MODULE
封裝: EIGTH BRICK PACKAGE-10
文件頁(yè)數(shù): 4/9頁(yè)
文件大?。?/td> 1008K
代理商: LEN-1/28-D12M
N O N - I S O L A T E D , 2 8 A E I G H T H B R I C K , D C / D C C O N V E R T E R S
LEN D12 Models
elements and should be selected for bulk capacitance, low ESR, and appro-
priate frequency response. Any scope measurements of PARD should be
made directly at the DC/DC output pins with scope probe ground less than
0.5" in length.
All external capacitors should have appropriate voltage ratings and be located
as close to the converters as possible. Temperature variations for all relevant
parameters should be taken into consideration.
The most effective combination of external I/O capacitors will be a function
of your line voltage and source impedance, as well as your particular load and
layout conditions. Our Applications Engineers can recommend potential solu-
tions and discuss the possibility of our modifying a given device’s internal lter-
ing to meet your specic requirements. Contact our Applications Engineering
Group for additional details.
Input Fusing
Most applications and or safety agencies require the installation of fuses
at the inputs of power conversion components. LEN D12 Series DC/DC
converters are not internally fused. Therefore, input fusing is mandatory for
safety reasons, and safety agencies require a time delay fuse with a value
no greater than 40Amps, which should be installed within the ungrounded
input path to the converter.
As a rule of thumb however, we recommend to use a normal-blow or slow-
blow fuse with a typical value of about twice the maximum input current,
calculated at low line with the converters minimum efciency.
4
Safety Considerations
LEN D12's are non-isolated DC/DC converters. In general, all DC/DC's
must be installed, including considerations for I/O voltages and spacing/
separation requirements, in compliance with relevant safety-agency speci-
cations (usually UL/IEC/EN60950).
In particular, for a non-isolated converter's output voltage to meet SELV
(safety extra low voltage) requirements, its input must be SELV compliant.
If the output needs to be ELV (extra low voltage), the input must be ELV.
Start-Up Time
The VIN to VOUT Start-Up Time is the interval between the time at which a
ramping input voltage crosses the lower limit of the specied input voltage
range (10.2 Volts) and the fully loaded output voltage enters and remains
within its specied accuracy band. Actual measured times will vary with input
source impedance, external input capacitance, and the slew rate and nal
value of the input voltage as it appears to the converter.
The On/Off to VOUT Start-Up Time assumes the converter is turned off via the
On/Off Control with the nominal input voltage already applied to the converter.
The specication denes the interval between the time at which the converter
is turned on and the fully loaded output voltage enters and remains within its
specied accuracy band. See Typical Performance Curves.
On/Off Control
The On/Off Control pin may be used for remote on/off operation. LEN D12
Series DC/DC converters are designed so that they are enabled when the
control pin is left open (or pulled low to 0 to +0.4V) and disabled when the
control pin is pulled high (+2.8V to +VIN). As shown in Figure 2, all models
have an internal 20k
pull-down resistor to Common (ground).
Dynamic control of the on/off function is best accomplished with a mechanical
relay or open-collector/open-drain drive circuit (optically isolated if appropri-
ate). The drive circuit should be able to sink appropriate current when
activated and withstand appropriate voltage when deactivated.
Figure 2. Driving the On/Off Control Pin
Remote Sense
LEN D12 Series DC/DC converters offer an output sense function on pin 10.
The sense function enables point-of-use regulation for overcoming moderate
IR drops in conductors and/or cabling. Since these are non-isolated devices
whose inputs and outputs usually share the same ground plane, sense is
provided only for the +Output.
The on/off control can be driven using a circuit comparable to that shown in
Figure 2. Leaving the On/Off control pin open or applying a voltage between
0V and +0.4V will turn on the converter. Applied voltages between +2.8V and
+VIN will disable the converter.
The remote sense line is part of the feedback control loop regulating the
DC/DC converter’s output. The sense line carries very little current and
consequently requires a minimal cross-sectional-area conductor. As such,
it is not a low-impedance point and must be treated with care in layout and
cabling. Sense lines should be run adjacent to signals (preferably ground),
and in cable and/or discrete-wiring applications, twisted-pair or similar
techniques should be used. To prevent high frequency voltage differences
between VOUT and Sense, we recommend installation of a 1000pF capacitor
close to the converter.
The sense function is capable of compensating for voltage drops between the
+Output and +Sense pins that do not exceed 10% of VOUT.
[VOUT(+) – Common] – [Sense(+) – Common]
≤ 10%VOUT
Power derating (output current limiting) is based upon maximum output
current and voltage at the converter's output pins. Use of trim and sense
functions can cause the output voltage to increase, thereby increasing output
power beyond the converter's specied rating. Therefore:
(VOUT at pins) x (IOUT)
≤ rated output power
The internal 10.5
resistor between +Sense and +Output (see Figure 1)
serves to protect the sense function by limiting the output current owing
through the sense line if the main output is disconnected. It also prevents
output voltage runaway if the sense connection is disconnected.
Note: If devices have the +Sense pin (pin 10) installed (no part-number
sufx) and the sense function is not used for remote regulation, +Sense
(pin 10) must be tied to +Output (pin 7, 9) at the DC/DC converter pins.
ON/OFF pin open: Logic Low = DC/DC converter On
ON/OFF pin >2.8V: Logic High = DC/DC converter Off
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