Texas Instruments LM3429 Evaluation Boards LM3429BKBSTEVAL/NOPB LM3429BKBSTEVAL/NOPB Datenbogen
Produktcode
LM3429BKBSTEVAL/NOPB
2
OV
HYSO
R
A
20
V
x
P
=
¸
¸
¹
¹
·
¨
¨
©
©
§
x
=
- OFF
TURN
24V
.
1
V
x
+
OV1
OV2
R
5
.
0
R
1
OV
R
1
¸
¸
¹
¹
·
¨
¨
©
©
§
x
=
- OFF
TURN
24V
.
1
V
1
OV
R
+
2
OV
OV
R
R
LM3429
OVP
R
OV2
R
OV1
LED+
LED-
SNVS616G – APRIL 2009 – REVISED MAY 2013
The LM3429 can be configured to detect an output (or input) over-voltage condition via the OVP pin. The pin
features a precision 1.24V threshold with 20 µA (typical) of hysteresis current as shown in
features a precision 1.24V threshold with 20 µA (typical) of hysteresis current as shown in
. When the
OVLO threshold is exceeded, the GATE pin is immediately pulled low and a 20 µA current source provides
hysteresis to the lower threshold of the OVLO hysteretic band.
hysteresis to the lower threshold of the OVLO hysteretic band.
If the LEDs are referenced to a potential other than ground (floating), as in the buck-boost and buck
configuration, the output voltage (V
configuration, the output voltage (V
O
) should be sensed and translated to ground by using a single PNP as
shown in
Figure 24. Floating Output OVP Circuitry
The over-voltage turn-off threshold (V
TURN-OFF
) is defined as follows:
Ground Referenced
(20)
Floating
(21)
In the ground referenced configuration, the voltage across R
OV2
is V
O
- 1.24V whereas in the floating
configuration it is V
O
- 620 mV where 620 mV approximates the V
BE
of the PNP transistor.
The over-voltage hysteresis (V
HYSO
) is defined as follows:
(22)
INPUT UNDER-VOLTAGE LOCKOUT (UVLO)
The nDIM pin is a dual-function input that features an accurate 1.24V threshold with programmable hysteresis as
shown in
shown in
. This pin functions as both the PWM dimming input for the LEDs and as a V
IN
UVLO. When
the pin voltage rises and exceeds the 1.24V threshold, 20 µA (typical) of current is driven out of the nDIM pin into
the resistor divider providing programmable hysteresis.
the resistor divider providing programmable hysteresis.
Copyright © 2009–2013, Texas Instruments Incorporated
17
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