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PDF NCV4279 Data sheet ( Hoja de datos )
| Número de pieza | NCV4279 | |
| Descripción | 5.0 V Micropower 150 mA LDO Linear Regulator with DELAY / Adjustable RESET / and Monitor FLAG | |
| Fabricantes | ON | |
| Logotipo |  |
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NCV4279
5.0 V Micropower 150 mA
LDO Linear Regulator with
DELAY, Adjustable RESET,
and Sense Output
The NCV4279 is a 5.0 V precision micropower voltage regulator
with an output current capability of 150 mA.
The output voltage is accurate within ±2.0% with a maximum
dropout voltage of 0.5 V at 100 mA. Low quiescent current is a feature
drawing only 150 mA with a 1.0 mA load. This part is ideal for any and
all battery operated microprocessor equipment.
Microprocessor control logic includes an active reset output RO
with delay and a SI/SO monitor which can be used to provide an early
warning signal to the microprocessor of a potential impending reset
signal. The use of the SI/SO monitor allows the microprocessor to
finish any signal processing before the reset shuts the microprocessor
down.
The active Reset circuit operates correctly at an output voltage as
low as 1.0 V. The Reset function is activated during the power up
sequence or during normal operation if the output voltage drops
outside the regulation limits.
The reset threshold voltage can be decreased by the connection of an
external resistor divider to the RADJ lead. The regulator is protected
against reverse battery, short circuit, and thermal overlowawdw.DcaotaSnhdeeitt4iUo.conms.
The device can withstand load dump transients making it suitable for
use in automotive environments. The device has also been optimized
for EMC conditions.
If the application requires pullup resistors at the logic outputs Reset
and Sense Out, the NCV4269 with integrated resistors can be used.
Features
• 5.0 V ± 2.0% Output
• Low 150 mA Quiescent Current
• Active Reset Output Low Down to VQ = 1.0 V
• Adjustable Reset Threshold
• 150 mA Output Current Capability
• Fault Protection
♦ +60 V Peak Transient Voltage
♦ −40 V Reverse Voltage
♦ Short Circuit
♦ Thermal Overload
• Early Warning through SI/SO Leads
• Internally Fused Leads in SO−14 Package
• Very Low Dropout Voltage
• Electrical Parameters Guaranteed Over Entire Temperature Range
• Pb−Free Packages are Available
• NCV Prefix for Automotive and Other Applications Requiring Site
and Control Changes
http://onsemi.com
8
1
SO−8
D SUFFIX
CASE 751
MARKING
DIAGRAMS
8
4279
ALYW
G
1
14
1
SO−14
D SUFFIX
CASE 751A
14
NCV4279
AWLYWWG
1
A = Assembly Location
WL, L = Wafer Lot
YY, Y = Year
WW, W = Work Week
G, G = Lead Free Indicators
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 12 of this data sheet.
© Semiconductor Components Industries, LLC, 2005
December, 2005 − Rev. 3
1
Publication Order Number:
NCV4279/D
1 page  
II
1000 mF
CI
470 nF
VI
VSI
NCV4279
I
ISI
SI
D
GND RO
IQ
Q
RADJ1
RADJ
SO
IRADJ
CQ
22 mF
RSO RRO
VQ
ID Iq VRO VSO
VRADJ
CD
100 nF
VD
RADJ2
Figure 2. Measuring Circuit
VI
VQ
VRT
VD
VUD
VLD
VRO
VRO,SAT
td
Power−on−Reset
< tRR
dV
dt
+
ID
CD
tRR
Thermal
Shutdown
Voltage Dip
at Input
Undervoltage
Secondary Overload
Spike at Output
Figure 3. Reset Timing Diagram
t
t
t
t
http://onsemi.com
5
5 Page 
NCV4279
SENSE INPUT (SI) / SENSE OUTPUT (SO) VOLTAGE
MONITOR
An on−chip comparator is available to provide early
warning to the microprocessor of a possible reset signal. The
output is from an open collector driver. The reset signal
typically turns the microprocessor off instantaneously. This
can cause unpredictable results with the microprocessor.
The signal received from the SO pin will allow the
microprocessor time to complete its present task before
shutting down. This function is performed by a comparator
referenced to the band gap voltage. The actual trip point can
be programmed externally using a resistor divider to the
input monitor SI (Figure 18). The values for RSI1 and RSI2
are selected for a typical threshold of 1.20 V on the SI Pin.
SIGNAL OUTPUT
Figure 19 shows the SO Monitor timing waveforms as a
result of the circuit depicted in Figure 18. As the output
voltage (VQ) falls, the monitor threshold (VSILOW), is
crossed. This causes the voltage on the SO output to go low
sending a warning signal to the microprocessor that a reset
signal may occur in a short period of time. TWARNING is the
time the microprocessor has to complete the function it is
currently working on and get ready for the reset
shutdown signal.
VQ
SI
VSILOW
VRO
SO
TWARNING
Figure 19. SO Warning Waveform Time Diagram
STABILITY CONSIDERATIONS
The input capacitor CI in Figure 18 is necessary for
compensating input line reactance. Possible oscillations
caused by input inductance and input capacitance can be
damped by using a resistor of approximately 1.0 W in series
with CI.
The output or compensation capacitor helps determine
three main characteristics of a linear regulator: startup delay,
load transient response and loop stability.
The capacitor value and type should be based on cost,
availability, size and temperature constraints. A tantalum or
aluminum electrolytic capacitor is best, since a film or
ceramic capacitor with almost zero ESR can cause
instability. The aluminum electrolytic capacitor is the least
expensive solution, but, if the circuit operates at low
temperatures (−25°C to −40°C), both the value and ESR of
the capacitor will vary considerably. The capacitor
manufacturer’s data sheet usually provides this information.
The value for the output capacitor CQ shown in Figure 18
should work for most applications; however, it is not
necessarily the optimized solution. Stability is guaranteed at
values CQ = 10 mF and an ESR = 10 W within the operating
temperature range. Actual limits are shown in a graph in the
typical data section.
CALCULATING POWER DISSIPATION IN A SINGLE
OUTPUT LINEAR REGULATOR
The maximum power dissipation for a single output
regulator (Figure 18) is:
PD(max) + [VI(max) * VQ(min)] IQ(max) ) VI(max) Iq (eq. 4)
where:
VI(max) is the maximum input voltage,
VQ(min) is the minimum output voltage,
IQ(max) is the maximum output current for the application,
and Iq is the quiescent current the regulator consumes at
IQ(max).
Once the value of PD(max) is known, the maximum
permissible value of RqJA can be calculated:
RqJA = (150°C – TA) / PD
(eq. 5)
The value of RqJA can then be compared with those in the
package section of the data sheet. Those packages with
RqJA’s less than the calculated value in equation 2 will keep
the die temperature below 150°C. In some cases, none of the
packages will be sufficient to dissipate the heat generated by
the IC, and an external heatsink will be required. The current
flow and voltages are shown in the
Measurement Circuit Diagram.
HEATSINKS
A heatsink effectively increases the surface area of the
package to improve the flow of heat away from the IC and
into the surrounding air.
Each material in the heat flow path between the IC and the
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of RqJA:
RqJA + RqJC ) RqCS ) RqSA
(eq. 6)
where:
RqJC = the junction−to−case thermal resistance,
RqCS = the case−to−heat sink thermal resistance, and
RqSA = the heat sink−to−ambient thermal resistance.
RqJC appears in the package section of the data sheet. Like
RqJA, it too is a function of package type. RqCS and RqSA are
functions of the package type, heatsink and the interface
between them. These values appear in data sheets of
heatsink manufacturers. Thermal, mounting, and
heatsinking considerations are discussed in the
ON Semiconductor application note AN1040/D, available
on the ON Semiconductor website.
http://onsemi.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet NCV4279.PDF ] | |
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