Datasheet

R4 =
(V
OVH
- 2.5V)
2.5V x R3
R3 =
V
OVH
- V
OVL
22 PA
=
V
OV(HYS)
22 PA
R2 =
(V
UVL
- 2.5V)
2.5V x R1
R1 =
V
UVH
- V
UVL
22 PA
=
V
UV(HYS)
22 PA
VCC
OVLO
VEE
TIMER AND GATE
LOGIC CONTROL
GND
VEE
To Load
Vee
Vee
Vee
R4
LM5067
22 PA
C
IN
R
IN
V
SYS
R2
R1
R3
UVLO/EN
2.50V
2.50V
22 PA
LM5067
SNVS532C –OCTOBER 2007–REVISED MARCH 2013 www.ti.com
Figure 15. Programming the Four Thresholds
The four resistor values are calculated as follows:
• Determine the upper UVLO threshold (V
UVH
) to enable Q1, and the lower UVLO threshold (V
UVL
) to disable
Q1.
(14)
• Determine the upper OVLO threshold (V
OVH
) to disable Q1, and the lower OVLO threshold (V
OVL
) to enable
Q1.
(15)
As an example, assume the application requires the following thresholds: V
UVH
= -22V, V
UVL
= -17V, V
OVH
= -
60V, and V
OVL
= -58V. Therefore V
UV(HYS)
= 5V, and V
OV(HYS)
= 2V. The resistor values are:
R1 = 227 kΩ, R2 = 39.1 kΩ
R3 = 90.9 kΩ, R4 = 3.95 kΩ
Where the R1-R4 resistor values are known, the threshold voltages and hysteresis are calculated from the
following:
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