Datasheet

V
OVL
= 1.16V + [R3 x (1.16V - 20 PA)]
R4
V
OVH
=
1.16V x (R3 + R4)
R4
V
UVL
=
1.17V x (R1 + R2)
R2
V
UVH
= 1.17V + [R1 x (1.17V + 20 PA)]
R2
R4 =
(V
OVH
- 1.16V)
1.16V x R3
R3 =
V
OVH
- V
OVL
20 PA
=
V
OV(HYS)
20 PA
R2 =
(V
UVL
- 1.17V)
1.17V x R1
R1 =
V
UVH
- V
UVL
20 PA
=
V
UV(HYS)
20 PA
VIN
UVLO
OVLO
GND
R3
R2
R1
TIMER AND GATE
LOGIC CONTROL
LM25069
V
SYS
R4
20 PA
1.17V
1.16V
20 PA
V
OVL
= [(R1 + R2) x ((1.16V) - 20 PA)] + 1.16V
R3
V
OVH
=
1.16V x (R1 + R2 + R3)
R3
LM25069
www.ti.com SNVS607E –FEBRUARY 2011–REVISED MARCH 2013
(21)
(22)
V
OV(HYS)
= (R1 + R2) x 20 µA (23)
Option B: If all four thresholds must be accurately defined, the configuration in Figure 32 can be used.
Figure 32. Programming the Four Thresholds
The four resistor values are calculated as follows:
• Choose the upper and lower UVLO thresholds (V
UVH
) and (V
UVL
).
(24)
(25)
• Choose the upper and lower OVLO threshold (V
OVH
) and (V
OVL
).
(26)
(27)
As an example, assume the application requires the following thresholds: V
UVH
= 8V, V
UVL
= 7V, V
OVH
= 15.5V,
and V
OVL
= 14V. Therefore V
UV(HYS)
= 1V, and V
OV(HYS)
= 1.5V. The resistor values are:
R1 = 50 kΩ, R2 = 10 kΩ
R3 = 75 kΩ, R4 = 6.07 kΩ
Where the R1-R4 resistor values are known, the threshold voltages and hysteresis are calculated from the
following:
(28)
(29)
V
UV(HYS)
= R1 x 20 µA (30)
(31)
(32)
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