LM5067MM-1 NSC [National Semiconductor], LM5067MM-1 Datasheet - Page 18

• Manufacturer Part Number: LM5067MM-1
• Description: Negative Hot Swap / Inrush Current Controller with Power Limiting
• Manufacturer: NSC [National Semiconductor]

www.national.com
The procedure to calculate the resistor values is as follows:
Q1, and the lower UVLO threshold (V
Q1.
be chosen in advance in this case, but is determined after the
values for R1-R3 are determined. If V
defined in addition to the other three thresholds, see Option
B below.
The resistors are calculated as follows:
The lower OVLO threshold is calculated from:
As an example, assume the application requires the following
thresholds: V
The lower OVLO threshold calculates to -55.8V, and the OV-
LO hysteresis is 4.2V. Note that the OVLO hysteresis is
always slightly greater than the UVLO hysteresis in this con-
figuration.
When the R1-R3 resistor values are known, the threshold
voltages and hysteresis are calculated from the following:
- The lower OVLO threshold (V
- Determine the upper OVLO threshold (V
- Determine the upper UVLO threshold (V
UVH
= -36V, V
UVL
= -32V, V
OVL
), to enable Q1, cannot
UVL
OVL
OVH
) to disable Q1.
must be accurately
= -60V.
OVH
UVH
) to disable
) to enable
18
Note: Ensure the voltages at the UVLO and OVLO pins do
not exceed the Absolute Maximum ratings for those pins
when the system voltage is at maximum.
Option B: If all four thresholds must be accurately defined,
the configuration in Figure 12 can be used.
The four resistor values are calculated as follows:
and the lower UVLO threshold (V
Q1, and the lower OVLO threshold (V
- Determine the upper UVLO threshold (V
- Determine the upper OVLO threshold (V
FIGURE 12. Programming the Four Thresholds
UVL
) to disable Q1.
OVL
) to enable Q1.
UVH
OVH
) to enable Q1,
) to disable
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