Datasheet

V
OVL
= [(R1 + R2) x ((2.5V) - 21 PA)] + 2.5V
R3
R2 =
2.5V x R1
(V
UVL
- 2.5V)
- R3
R3 =
2.5V x R1 x V
UVL
V
OVH
x (V
UVL
- 2.5V)
R1 =
V
UVH
- V
UVL
21 PA
UVLO
OVLO
R1
TP1
4
3
95.3k
R2
4.64k
R3
3.32k
Note: R4 = open
LM5069
V
IN
UVLO/OVLO Input Voltage Thresholds www.ti.com
The waveform at the TIMER pin can be monitored at the test pad located between C8 and R9. In this
evaluation board, the fault timeout period is ≊38 ms, and the restart time is ≊7.7 seconds. See Figures 11
and 12.
8 UVLO/OVLO Input Voltage Thresholds
As supplied, the input voltage UVLO thresholds on this evaluation board are approximately 34.4V
increasing, and 32.4V decreasing. The OVLO thresholds are approximately 77.7V increasing, and 75.7V
decreasing. The four thresholds are determined by resistors R1-R4. The threshold voltage at each pin is
2.50V, and internal 21µA current sources provide hysteresis for each threshold. See the device data sheet
for more details.
Option A: This evaluation board is supplied with the jumper at JMP1 on pins 2-3, resulting in the
configuration shown in Figure 5.
Figure 5. UVLO, OVLO Inputs (Option A)
To change the thresholds in this configuration, resistors R1-R3 are calculated using the following
procedure:
• Choose the upper UVLO threshold (V
UVH
), and the lower UVLO threshold (V
UVL
).
• Choose the upper OVLO threshold (V
OVH
)
The lower OVLO threshold (V
OVL
) cannot be chosen in advance in this case, but is determined after the
values for R1-R3 are determined. If V
OVL
must be accurately defined in addition to the other three
thresholds, see Option B below.
The resistors are calculated as follows:
(6)
(7)
(8)
The lower OVLO threshold is calculated from:
(9)
Option B: If all four thresholds must be determined accurately, move the jumper at JMP1 to pins 1-2, and
add R4, resulting in the configuration shown in Figure 6.
6
AN-1522 LM5069 Evaluation Board SNVA184B–September 2006–Revised May 2013
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