ncv4279c ON Semiconductor, ncv4279c Datasheet - Page 8

• Manufacturer Part Number: ncv4279c
• Description: 5.0 V Micropower 150 Ma Ldo Linear Regulator With Delay, Adjustable Reset, And Monitor Flag
• Manufacturer: ON Semiconductor

FLAG Monitor
of the circuit depicted in Figure 13. As the output voltage
falls (V
the voltage on the FLAG output to go low sending a warning
signal to the microprocessor that a RESET signal may occur
in a short period of time. T
microprocessor has to complete the function it is currently
working on and get ready for the RESET shutdown signal.
Voltage, Delay Switching Threshold, and the Delay Charge
Current. The delay follows the equation:
Example:
three main characteristics of a linear regulator: startup delay,
load transient response and loop stability.
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.
RESET
FLAG
V
MON
Ref. Voltage
OUT
t DELAY =
Figure 14 shows the FLAG Monitor waveforms as a result
The delay time is controlled by the Reset Delay Low
Using C
Use the typical value for Delay Low Voltage = 0.45 V.
Use the typical value for V
Use the typical value for Delay Charge Current = 2.5 mA.
The output or compensation capacitor helps determine
The capacitor value and type should be based on cost,
Figure 14. FLAG Monitor Circuit Waveform
t DELAY =
OUT
DELAY
STABILITY CONSIDERATIONS
), the Monitor threshold is crossed. This causes
SETTING THE DELAY TIME
[ C DELAY (V dt − Reset Delay Low Voltage) ]
= 33 nF.
[ 33 nF(1.8 − 0.45 V) ]
FLAG MONITOR
Delay Charge Current
2.5 mA
T
dt
WARNING
WARNING
= 1.8 V.
= 17.8 ms
is the time the
APPLICATION NOTES
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8
*C
should work for most applications, but is not necessarily the
optimized solution.
regulator (Figure 16) is:
P D(max) = [V IN(max) − V OUT(min) ] I OUT(max)
where:
permissible value of R
package section of the data sheet. Those packages with
R
the die temperature below 150°C.
dissipate the heat generated by the IC, and an external
heatsink will be required.
V
**C
IN
θJA
0.1 mF
IN
The value for the output capacitor C
The maximum power dissipation for a single output
V
V
I
application, and
I
I
Once the value of P
The value of R
In some cases, none of the packages will be sufficient to
C
OUT(max)
Q
OUT(max)
OUT
Figure 15. Test and Application Circuit Showing
IN(max)
OUT(min)
IN
CALCULATING POWER DISSIPATION IN A
required if regulator is located far from the power supply filter.
’s less than the calculated value in equation 2 will keep
is the quiescent current the regulator consumes at
V
Figure 16. Single Output Regulator with Key
*
SINGLE OUTPUT LINEAR REGULATOR
IN
required for stability. Capacitor must operate at minimum
Performance Parameters Labeled
is the maximum input voltage,
.
+ V IN(max) I Q
is the minimum output voltage,
is the maximum output current for the
I
IN
θJA
Output Compensation
NCV4279C
R θJA = 150˚C −
temperature expected.
can then be compared with those in the
θJA
REGULATOR®
RESET
D(max)
}
can be calculated:
V
SMART
Control
Features
OUT
P D
is known, the maximum
I
Q
OUT
T A
R
RST
shown in Figure 15
I
OUT
C
10 mF
OUT
V
OUT
**
(1)
(2)