ncv8881 ON Semiconductor, ncv8881 Datasheet - Page 21

• Manufacturer Part Number: ncv8881
• Description: Ncv8881 1.5a Automotive Buck Regulator With Watchdog
• Manufacturer: ON Semiconductor

parallel with RPDOWN making the internal resistance from
the EN pin to ground lower than when the EN pin is above
V
when there is resistance between the source of the Enable
signal and the EN pin. A resistive divider from the Enable
signal source to the EN pin (Figure 44) allows a wide range
of activation/deactivation voltages. Note that this divider is
also used in conjunction with an internal zener clamp to keep
the EN pin voltage below the maximum voltage rating when
ENSTHH
When the EN pin is below V
. This produces hysteresis in the Enable function
7
6
5
4
3
2
1
0
2
Figure 45. Enable Input VILmax Programming Range versus VIH
2.5
EXTERNAL
RESISTORS
NCV8881 Enable Input VILmax Programming Range versus VIHmin Setting
ENSTHL
R1
R2
ENABLE
SIGNAL
3
Figure 44. Enable Input Hysteresis Mechanism
EN
PIN
, RHYST is in
3.5
CLAMP
http://onsemi.com
VIHmin Setting (V)
4
NCV8881
MUST BE OFF
21
RPDOWN
1MEG
battery is the enable signal. Given the lowest voltage that
must enable the part VIH
must disable the part VIL
are:
R1 = 0.7874 * (VIL
[R2 in kW]
R2 = 1800*(1.2283 * VIL
86.823 * VIL
Minimum hysteresis is: 0.0415 * R1 [V] [R1 in kW]
RHYST
4.5
30K
THRESHOLD
MAX
5
COMPARATOR
+ 108.7) [kW]
MAX
5.5
min
MIN
– 1.27)/(0.0005556 * 1/R2) [kW]
MAX
MAX
Setting
, and the highest voltage that
the divider resistor values
− VIH
6
MIN
)/( VIH
6.5
MIN
–