Texas Instruments LM3423 Evaluation Board LM3423BBLSCSEV/NOPB LM3423BBLSCSEV/NOPB Datenbogen
Produktcode
LM3423BBLSCSEV/NOPB
IS
AGND
PWM
Start new on time
nDIM
COMP
REFERENCE
CURRENT
LIMIT
CSH
HSN
LOGIC
HSP
EN
OVP
HYSTERESIS
LED CURRENT LOW
S
R
Q
UVLO
DDRV
GATE
PGND
OVP
LRDY
RPD
EN
LatchOff
TIMR
OVLO
FLT
LED CURRENT HIGH
Regulator
Thermal
Limit
TLIM
TLIM
OVLO
PGND
LatchOff
Standby
Dimming
Reset
Dominant
RCT
800 mV
S
T
O
P
820k
500k
LEB
In the LM3421, TIMR is internally shorted to AGND.
1.235V
6.9V LDO
(4.1V)
DPOL
Grey pins are available in the LM 3423 only.
LEB
W
= 150 ns
V
IN
/25
V
IN
UVLO
HYSTERESIS
1.24V
V
CC
1.235V
V
CC
1.24V
1.24V
0.245V
1.0V
1.6V
V
CC
UVLO
V
CC
V
CC
UVLO
V
IN
23
P
A
23
P
A
11.5
P
A
SNVS574E – JULY 2008 – REVISED MAY 2013
BLOCK DIAGRAM
THEORY OF OPERATION
The LM3421/23 are N-channel MosFET (NFET) controllers for buck, boost and buck-boost current regulators
which are ideal for driving LED loads. The controller has wide input voltage range allowing for regulation of a
variety of LED loads. The high-side differential current sense, with low adjustable threshold voltage, provides an
excellent method for regulating output current while maintaining high system efficiency. The LM3421/23 uses a
Predictive Off-time (PRO) control architecture that allows the regulator to be operated using minimal external
control loop compensation, while providing an inherent cycle-by-cycle current limit. The adjustable current sense
threshold provides the capability to amplitude (analog) dim the LED current and the output enable/disable
which are ideal for driving LED loads. The controller has wide input voltage range allowing for regulation of a
variety of LED loads. The high-side differential current sense, with low adjustable threshold voltage, provides an
excellent method for regulating output current while maintaining high system efficiency. The LM3421/23 uses a
Predictive Off-time (PRO) control architecture that allows the regulator to be operated using minimal external
control loop compensation, while providing an inherent cycle-by-cycle current limit. The adjustable current sense
threshold provides the capability to amplitude (analog) dim the LED current and the output enable/disable
10
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