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參數(shù)資料
| 型號： | RC4190M |
| 廠商： | Raytheon Company |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | RADIATION HARDENED HIGH EFFICIENCY, 5 AMP SWITCHING REGULATORS |
| 中文描述： | 抗輻射高效，5安培開關(guān)穩(wěn)壓器 |
| 文件頁數(shù)： | 14/25頁 |
| 文件大?。?/td> | 174K |
| 代理商： | RC4190M |
PRODUCT SPECIFICATION
RC4190
14
The threshold is programmed exactly as the noram low bat-
tery detector connection:
When the battery voltage reaches this threshold, the compar-
ator will turn on the open collector transistor at pin 8, effec-
tively putting C2 in parallel with C
X
. This added capacitance
will reduce the oscillator frequency according to the follow-
ing equation:
Where C is in pF and F
O
is in Hz.
Component values for a typical application might be R2 =
330 k
, R5 = 150 k
, C
X
= 100 pF, and C2 = 100 pF. These
values would set the threshold voltage at 4.1V and change
the operating frequency from 48 kHz to 24 kHz. Note that
this technique may be used for step-up, step-down, or invert-
ing applications.
Step-Down Regulator With Protection
One disadvantage of the simple application circuits is their
lack of short circuit protection, especially for the step-up cir-
cuit, which has a very low resistance path for current flow
from the input to the output. A current limiting circuit which
senses the output voltage and shuts down the 4190 if the out-
put voltage drops too low can be built using the low battery
detector circuitry. The low battery detector is connected to
sense the output voltage and will shut off the oscillator by
forcing pin 2 low if the output voltage drops. Figure 20
V
TH
V
REF
R5
R4
1
+
=
F
O
C
X
10
C2
+
6
–
×
2.4
=
shows a schematic of a step-down regulator with this
connection.
R2 and R3 set the output voltage, as in the circuit of Figure
2. Choose resistor values so R5 = R3 and R4 = R2, and make
R8 25 to 35 times higher than R3. When the output is
shorted, the open collector transistor at pin 8 will force pin 2
low and shut off the oscillator and therefore shut off the
external switch transistor. The regulator will then remain in a
low current off condition until power is removed and reap-
plied. C2 provides momentary current to ensure proper start-
up. This scheme will not work with the simple step-up regu-
lator, but will work with the boost-buck converter, providing
short circuit protection in both step-up and step-down
modes.
RC4190/RC4391
±
Power Supply
A positive and negative dual tracking power supply using a
step-up RC4190 and an inverting RC4391 is shown in Figure
21. The inductor and capacitor values were chosen to achieve
the highest practical output currents from a +12V battery, as
it decays, while keeping the output voltage ripple under 100
mV
p-p
at
±
15V output.
The circuit may be adapted to other voltages and currents,
but note that the RC4190 is step-up, so V
OUT
must be
greater than V
BAT
.
The output voltages may both be trimmed by adjusting a
single resistor value (R3 or R4), because the reference for the
negative output is derived from +V
OUT
. This connection also
allows the output voltages to track each other with changes
in temperature and line voltage.
Figure 21. Step-Down Regulator with Protection
V
BAT
65-2684
4190
7
3
5
6
Lx
+V
OUT
2N3635
2
Cx
R4
R1
1M
R5
1N914
R3
R2
1
8
R6
1.0K
C2
10
μ
F
R8
V = 1.31 ( R3
R8 = 35(R3)
C
F
I
C
+V
S
V
FB
LBR
Gnd
LBD
C
X
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