LM3424 Datasheet, PDF (3/69 Pages) National Semiconductor (TI) – Constant Current N-Channel Controller with Thermal Foldback for Driving LEDs

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5 Pin Configuration and Functions
LM3424, LM3424-Q1
SNVS603C – AUGUST 2009 – REVISED AUGUST 2015
PWP Package
20-Pin HTSSOP With PowerPAD™
Top View
V_IN 1
EN 2
COMP 3
CSH 4
RT 5
nDIM 6
SS 7
TGAIN 8
TSENSE 9
TREF 10
21
DAP
20 HSP
19 HSN
18 SLOPE
17 IS
16 VCC
15 GATE
14 GND
13 DDRV
12 OVP
11 VS
PIN
NO. NAME
1
V_IN
I/O
I Input Voltage
2
EN
I Enable
3
COMP
I Compensation
4
CSH
I Current Sense High
5
RT
I Resistor Timing
6
nDIM
I
Dimming Input /
Under-Voltage Protection
7
SS
I Soft-start
8
TGAIN
I Temp Foldback Gain
9 TSENSE I Temp Sense Input
10
TREF
I Temp Foldback Reference
11
V_S
O Voltage Reference
12
OVP
I Over-Voltage Protection
13 DDRV O Dimming Gate Drive Output
14
GND GND Ground
15 GATE O Main Gate Drive Output
16
V_CC
O Internal Regulator Output
17
IS
I Main Switch Current Sense
18 SLOPE I Slope Compensation
19
HSN
I LED Current Sense Negative
20
DAP
HSP
DAP
I LED Current Sense Positive
GND Thermal pad on bottom of IC
Pin Functions
DESCRIPTION
Bypass with 100 nF capacitor to GND as close to the device as
possible.
Connect to > 2.4V to enable the device or to < 0.8V for low power
shutdown.
Connect a capacitor to GND to compensate control loop.
Connect a resistor to GND to set the signal current. Can also be used to
analog dim as explained in the Thermal Foldback and Analog Dimming
section.
Connect a resistor to GND to set the switching frequency. Can also be
used to synchronize to an external clock as explained in the Switching
Frequency section.
Connect a PWM signal for dimming as detailed in the PWM Dimming
section and/or a resistor divider from V_IN to program input under-voltage
lockout.
Connect a capacitor to GND to extend start-up time.
Connect a resistor to GND to set the foldback slope.
Connect a resistor/ thermistor divider from V_S to sense the temperature
as explained in the Thermal Foldback and Analog Dimming section.
Connect a resistor divider from V_S to set the foldback reference voltage.
2.45V reference for temperature foldback circuit and other external
circuitry.
Connect a resistor divider from V_O to program output over-voltage
lockout.
Connect to gate of dimming MOSFET.
Connect to DAP to provide proper system GND
Connect to gate of main switching MOSFET.
Bypass with a 2.2 µF – 3.3 µF ceramic capacitor to GND.
Connect to the drain of the main N-channel MOSFET switch for R_DS-ON
sensing or to a sense resistor installed in the source of the same device.
Connect a resistor to GND to set slope of additional ramp.
Connect through a series resistor to LED current sense resistor
(negative).
Connect through a series resistor to LED current sense resistor
(positive).
Connect to GND.
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Product Folder Links: LM3424 LM3424-Q1