Datasheet

GND
PGD
R
PG
LM5069
V
PGD
Power
Good
VIN
UVLO
OVLO
GND
TIMER AND GATE
LOGIC CONTROL
LM5069
21PA
21
PA
2.5V
2.5V
V
SYS
100k
R3
R4
Control
Restart
Shutdown/
V
OVL
= 2.5V + [R3 x (2.5V - 21 PA)]
R4
V
OVH
=
2.5V x (R3 + R4)
R4
V
UVL
=
2.5V x (R1 + R2)
R2
V
UVH
= 2.5V + [R1 x (2.5V + 21 PA)]
R2
LM5069
SNVS452D –SEPTEMBER 2006–REVISED MAY 2013 www.ti.com
V
UV(HYS)
= R1 x 21 µA
V
OV(HYS)
= R3 x 21 µA
Option C: The minimum UVLO level is obtained by connecting the UVLO pin to VIN as shown in Figure 35. Q1
is switched on when the VIN voltage reaches the POR
EN
threshold (≊8.4V). An external transistor can be
connected to UVLO to provide remote shutdown control, and to restart the LM5069-1 after a fault detection. The
OVLO thresholds are set using R3, R4. Their values are calculated using the procedure in Option B.
Figure 35. UVLO = POR
EN
with Shutdown/Restart Control
Option D: The OVLO function can be disabled by grounding the OVLO pin. The UVLO thresholds are set as
described in Option B or Option C.
POWER GOOD PIN
During turn-on, the Power Good pin (PGD) is high until the voltage at VIN increases above ≊ 5V. PGD then
switches low, remaining low as the VIN voltage increases. When the voltage at OUT increases to within 1.25V of
the SENSE pin (V
DS
<1.25V), PGD switches high. PGD switches low if the V
DS
of Q1 increases above 2.5V. A
pull-up resistor is required at PGD as shown in Figure 36. The pull-up voltage (V
PGD
) can be as high as 80V, with
transient capability to 100V, and can be higher or lower than the voltages at VIN and OUT.
Figure 36. Power Good Output
If a delay is required at PGD, suggested circuits are shown in Figure 37. In Figure 37a, capacitor C
PG
adds delay
to the rising edge, but not to the falling edge. In Figure 37b, the rising edge is delayed by R
PG1
+ R
PG2
and C
PG
,
while the falling edge is delayed a lesser amount by R
PG2
and C
PG
. Adding a diode across R
PG2
(Figure 37c)
allows for equal delays at the two edges, or a short delay at the rising edge and a long delay at the falling edge.
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