NCV8502 ON Semiconductor, NCV8502 Datasheet - Page 10

• Manufacturer Part Number: NCV8502
• Manufacturer: ON Semiconductor

Adding Capability
be used with an external pass transistor for additional current
capability. The setup as shown will provide greater than 1
Amp of output current.
of the circuit depicted in Figure 14. 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.
V
FLAG Monitor
RESET
FLAG
MON
Ref. Voltage
OUT
V
Figure 16 shows how the adjustable version of parts can
Figure 17 shows the FLAG Monitor waveforms as a result
BAT
Figure 17. FLAG Monitor Circuit Waveform
OUT
C2
0.1 mF
Figure 16. Additional Output Current
), the Monitor threshold is crossed. This causes
V
IN
NCV8502
FLAG MONITOR
V
ADJ
V
OUT
T
WARNING
294 k
100 k
WARNING
R1
R2
MJD31C
is the time the
>1 Amp
C1
47 mF
APPLICATION NOTES
NCV8502 Series
http://onsemi.com
5.0 V
10
Voltage, Delay Switching Threshold, and the Delay Charge
Current. The delay follows the equation:
Example:
three main characteristics of a linear regulator: start−up
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
manufacturers data sheet usually provides this information.
should work for most applications, however it is not
necessarily the optimized solution.
V
*C
**C
IN
t DELAY +
0.1 mF
The delay time is controlled by the Reset Delay Low
Using C
Assume reset Delay Low Voltage = 0.
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,
The value for the output capacitor C
IN
C
Figure 18. Test and Application Circuit Showing
OUT
IN
required if regulator is located far from the power supply filter
*
required for stability. Capacitor must operate at minimum
t DELAY +
DELAY
STABILITY CONSIDERATIONS
SETTING THE DELAY TIME
[ C DELAY (V dt * Reset Delay Low Voltage) ]
Output Compensation
= 33 nF.
NCV8502
temperature expected
[ 33 nF(1.8 * 0) ]
Delay Charge Current
RESET
2.5 mA
V
OUT
dt
= 1.8 V.
OUT
R
+ 23.8 ms
RST
shown in Figure 18
C
10 mF
OUT
**