AFL120XXS Series
Input Filter
The AFL120XXS series converters incorporate a LC input
filter whose elements dominate the input load impedance
characteristic at turn-on. The input circuit is as shown in
Figure IV.
Finding a resistor value for a particular output voltage, is
simply a matter of substituting the desired output voltage
and the nominal device voltage into the equation and solving
for the corresponding resistor value.
Figure V. Connection for VOUT Adjustment
Figure IV. Input Filter Circuit
Enable 2
16.8uH
Share
RADJ
Pin 1
+ Sense
AFL120xxS
- Sense
0.78uF
Return
To Load
+ Vout
Pin 2
Note: Radj must be set ≥ 500Ω
Attempts to adjust the output voltage to a value greater than
120% of nominal should be avoided because of the potential
of exceeding internal component stress ratings and
subsequent operation to failure. Under no circumstance
should the external setting resistor be made less than 500Ω.
By remaining within this specified range of values, completely
safe operation fully within normal component derating limits
is assured.
Undervoltage Lockout
A minimum voltage is required at the input of the converter
to initiate operation. This voltage is set to 74V ± 4.0V. To
preclude the possibility of noise or other variations at the
input falsely initiating and halting converter operation, a
hysteresis of approximately 7.0V is incorporated in this
circuit. Thus if the input voltage droops to 67V ± 4.0V, the
converter will shut down and remain inoperative until the
input voltage returns to ≈ 74V.
Examination of the equation relating output voltage and
resistor value reveals a special benefit of the circuit topology
utilized for remote sensing of output voltage in the
AFL120XXS series of converters. It is apparent that as the
resistance increases, the output voltage approaches the
nominal set value of the device. In fact the calculated limiting
value of output voltage as the adjusting resistor becomes
Output VoltageAdjust
In addition to permitting close voltage regulation of remotely
located loads, it is possible to utilize the converter sense
pins to incrementally increase the output voltage over a
limited range. The adjustments made possible by this method
are intended as a means to “trim” the output to a voltage
setting for some particular application, but are not intended
to create an adjustable output converter. These output
voltage setting variations are obtained by connecting an
appropriate resistor value between the +sense and -sense
pins while connecting the -sense pin to the output return pin
as shown in Figure V. below. The range of adjustment and
corresponding range of resistance values can be determined
very large is ≈ 25mV above nominal device voltage.
The consequence is that if the +sense connection is
unintentionally broken, an AFL120XXS has a fail-safe output
voltage of Vout + 25mV, where the 25mV is independent of
the nominal output voltage. It can be further demonstrated
that in the event of both the + and - sense connections
being broken, the output will be limited to Vout + 440mV.
This 440mV is also essentially constant independent of the
nominal output voltage.
by use of the following equation.
⎧
⎨
⎩
⎫
⎬
⎭
VNOM
Radj = 100•
VOUT - VNOM -.025
Where VNOM = device nominal output voltage, and
VOUT = desired output voltage
8
www.irf.com
5秒后页面跳转
SG3525资料手册详解：SG3525参数分析、引脚说明、应用介绍
AT89C51单片机资料手册详细解析及应用示例
CP2102资料手册解读：CP2102引脚说明、关键参数分析
资料手册解读：UC3842参数和管脚说明
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
