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PDF RC4190 Data sheet ( Hoja de datos )

Número de pieza RC4190
Descripción Micropower Switching Regulator
Fabricantes Fairchild 
Logotipo Fairchild Logotipo



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RC4190
Micropower Switching Regulator
www.fairchildsemi.com
Features
• High efficiency – 85% typical
• Low quiescent current – 215 mA
• Adjustable output – 1.3V to 30V
• High switch current – 200 mA
• Bandgap reference – 1.31V
• Accurate oscillator frequency – ±10%
• Remote shutdown capability
• Low battery detection circuitry
• Low component count
• 8-lead packages including small outline (SO-8)
Description
The RC4190 monolithic IC is a low power switch mode reg-
ulator intended for miniature power supply applications.
This DC-to-DC converter IC provides all of the active com-
ponents needed to create supplies for micropower circuits
(load power up to 400 mW, or up to 10W with an external
power transistor). Contained internally are an oscillator,
switch, reference, comparator, and logic, plus a discharged
battery detection circuit.
Application areas include on-card circuits where a non-standard
voltage supply is needed, or in battery operated instruments
where an RC4190 can be used to extend battery lifetime.
These regulators can achieve up to 85% efficiency in most
applications while operating over a wide supply voltage
range, 2.2V to 30V, at a very low quiescent current drain of
215 mA.
The standard application circuit requires just seven external
components for step-up operation: an inductor, a steering
diode, three resistors, a low value timing capacitor, and an
electrolytic filter capacitor. The combination of simple appli-
cation circuit, low supply current, and small package make
the RC4190 adaptable to a wide range of miniature power
supply applications.
The RC4190 is most suited for single ended step-up
(VOUT > VIN) circuits because the NPN internal switch tran-
sistor is referenced to ground. It is complemented by another
Fairchild Semiconductor micropower switching regulator,
the RC4391, which is dedicated to step-down (VOUT < VIN)
and inverting VOUT = –VIN) applications. Between the two
devices the ability to create all three basic switching regula-
tor configurations is assured. Refer to the RC4391 data sheet
for step-down and inverting applications.
Block Diagram
4190
LBR
C2
With some optional external components the application
circuit can be designed to signal a display when the battery
has decayed below a predetermined level, or designed to
signal a display at one level and then shut itself off after the
LBD battery decays to a second level. See the applications section
Q2 for these and other unique circuits.
CX OSC
Gnd
Q1
LX
C1
+1.31V
1.31V
REF
VFB
IC
+1.2V
BIAS
+VS
65-3464-01
The RC4190 micropower switching regulator series consists
of three devices, each with slightly different specifications.
The RM4190 has a 1.5% maximum output voltage tolerance,
0.2% maximum line regulation, and operation to 30V. The
RC4190 has a 5.0% maximum output voltage tolerance,
0.5% maximum line regulation, and operation to 24V. Other
specifications are identical. Each type is available in plastic
and ceramic DIPs, or SO-8 packages.
www.DataSheet4U.com
Rev. 1.0.0
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1 page




RC4190 pdf
RC4190
Typical Performance Characteristics
4.0
3.0
2.4V
2.0
1.0
2.0V
1.8V
0
-75 -50 -25
0 +25 +50 +75 +100 +125
TA (¡C)
Figure 1. Minimum Supply Voltage vs. Temperature
PRODUCT SPECIFICATION
300
250
230
200
215
195
150
100
50
0
-75 -50 -25
VS = +6V
0 +25 +50 +75 +100 +125
TA (¡C)
Figure 2. Quiescent Current vs. Temperature
1.33
1.32
1.31
1.30
1.29
1.28
-75 -50 -25
0 +25 +50 +75 +100 +125
TA (¡C)
Figure 3. Reference Voltage vs. Temperature
+2.0
+1.5
+1.0
+0.5
0
-0.5
-1.0
-1.5
-2.0
-75 -50 -25
0 +25 +50 +75 +100 +125
TA (¡C)
Figure 4. Oscillator Frequency vs. Temperature
+2
+1
0
-1
-2
0 5 10 15 20 25 30
+VS (V)
Figure 5. Minimum Supply Voltage vs. Temperature
5

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RC4190 arduino
RC4190
PRODUCT SPECIFICATION
+Vs
R4
1 LBR
LBD 8
C2
Q2
I LBD
R5
VREF
1.31V
65-1651
Figure 13. Low Battery Detector
When the battery voltage drops below this threshold Q2 will
turn on and sink over 1500 mA typically. The low battery
detector circuitry may also be used for other, less conven-
tional applications (see Figures 19 and 20).
Automatic Shutdown
The bias control current for the reference is externally set by
a resistor from the IC pin to the battery. This current can vary
from 1.0 mA to 50 mA without affecting the operation of the
IC. Interrupting this current will disable the entire circuit,
causing the output voltage to go to 0V for step-down appli-
cations, and reducing the supply current to less than 1.0 mA.
Automatic shutdown of the RC4190 can be achieved using
the circuit of Figure 14.
VBAT
5 +VS
R1
6 IC
R9
4190
GND
3
65-2678
Figure 14. Automatic Shutdown
A resistor is placed from the IC pin to ground, creating a
voltage divider. When the voltage at the IC pin is less than
1.2V, the RC4190 will begin to turn off. This scheme should
only be used in limited temperature range applications since
the “turn off” voltage at the IC pin has a temperature coeffi-
cient of -4.0 mV/°C. At 25°C, typically 250 nA is the mini-
mum current required by the IC pin to sustain operation.
A 5.0 mA voltage divider works well taking into account the
sustaining current of 250 nA and a threshold voltage of 0.4V
at turn off. As an example, if 3.0V is to be the turn off volt-
age, then R9 = 1.1/4.75 mA and R1 = (3.0 – 1.1) 5.0 mA or
about 240 kW and 390 kW respectively. The tempco at the
top of the divider will be -4.0 mV (R1 + R9)/R9 or
-10.5 mV/°C, an acceptable number for many applications.
Another method of automatic shutdown without temperature
limitations is the use of a zener diode in series with the IC
pin and set resistor. When the battery voltage falls below VZ
+ 1.2V the circuit will start to shut down. With this connec-
tion and the low battery detector, the application can be
designed to signal a display when the battery voltage has
dropped to the first programmed level, then shut itself off as
the battery reaches the zener threshold.
The set current can also be turned off by forcing the IC pin to
0.2V or less using an external transistor or mechanical
switch. An example of this is shown in Figure 15.
In this circuit an external control voltage is used to determine
the operating state of the RC4190. If the control voltage VC
is a logic 1 at the input of the 4025 (CMOS Triple NOR
Gate), the voltage at the IC pin will be less than 0.5V forcing
the 4190 off (<0.1 mA ICC). Both the 2N3904 and 2N2907
will be off insuring long shelf for the battery since less than
1.0 mA is drawn by the circuit.
When VC goes to a logic 0, 2.0 mA is forced into the IC pin
through the 2.2 MW resistor and the NOR gate, and at the
same time the 2N3904 and 2N2907 turn on, connecting the
battery to the load.
As long as VC remains low the circuit will regulate the
output to 5.0V. This type of circuit is used to back up the
main supply voltage when line interruptions occur, a particu-
larly useful feature when using volatile memory systems.
9.0V Battery Life Extender
Figure 16 shows a common application: a circuit to extend
the lifetime of a 9.0V battery. The regulator remains in its
quiescent state (drawing only 215 mA) until the battery volt-
age decays below 7.5V, at which time it will start to switch
and regulate the output at 7.0V until the battery falls below
2.2V.
If this circuit operates at its typical efficiency of 80%, with
an output current of 10 mA, at 5.0V battery voltage, then the
average input current will be IIN = (VOUT x IL) ¸ (VBAT x
ef) or (7.0V x 10 mA) ¸ (5.0V x 0.8 mA) = 17.5 mA.
Bootstrapped Operation (Step-Up)
In step-up applications, power to the RC4190 can be derived
from the output voltage by connecting the +VS pin and the
top of R1 to the output voltage (Figure 17).
One requirement for this circuit is that the battery voltage
must be greater than 3.0V when it is energized or else there
will not be enough voltage at pin 5 to start up the IC. The big
advantage of this circuit is the ability to operate down to a
discharged battery voltage of 1.0V.
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