Texas Instruments LM3429 Evaluation Boards LM3429BKBSTEVAL/NOPB LM3429BKBSTEVAL/NOPB Hoja De Datos
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LM3429BKBSTEVAL/NOPB
D1
OVP
LM3429
nDIM
PGND
NC
DAP
GATE
COMP
CSH
RCT
IS
HSN
HSP
L1
C
IN
C
BYP
Q1
C
CMP
R
CSH
C
T
R
UV2
R
UV1
1
2
3
4
5
6
7
14
13
12
11
10
9
8
R
HSN
R
HSP
1A
C
O
R
SNS
AGND
R
T
R
FS
C
FS
I
LED
Q2
R
OV2
R
OV1
C
OV
V
IN
V
IN
V
IN
10V
±
70V
V
IN
V
CC
R
LIM
(
)
R
R
+
x
2
UV
1
UV
A
20
P
(
)
x
HYS
A
20
V
x
P
-
R
2
UV
R
1
UV
UVH
R
=
SNVS616G – APRIL 2009 – REVISED MAY 2013
Method #2: If PWM dimming is required, a three resistor network is suggested. To set V
TURN-ON
, assume R
UV2
=
10 k
Ω
and solve for R
UV1
as in Method #1. To set V
HYS
, solve for R
UVH
:
(87)
13. PWM DIMMING METHOD
PWM dimming can be performed several ways:
Method #1: Connect the dimming MosFET (Q
3
) with the drain to the nDIM pin and the source to GND. Apply an
external PWM signal to the gate of Q
DIM
. A pull down resistor may be necessary to properly turn off Q
3
.
Method #2: Connect the anode of a Schottky diode to the nDIM pin. Apply an external inverted PWM signal to
the cathode of the same diode.
the cathode of the same diode.
14. ANALOG DIMMING METHOD
Analog dimming can be performed several ways:
Method #1: Place a potentiometer in series with the R
CSH
resistor to dim the LED current from the nominal I
LED
to near zero.
Method #2: Connect a controlled current source as detailed in the
section to the CSH pin.
Increasing the current sourced into the CSH node will decrease the LEDs from the nominal I
LED
to zero current.
Design Example #1
BUCK-BOOST APPLICATION - 6 LEDs at 1A
Copyright © 2009–2013, Texas Instruments Incorporated
31
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