PT4121E
60V Step-down High Brightness
LED Controller
GENERAL DESCRIPTION
The PT4121E is a high efficiency step-down
controller. It is designed to operate in continuous
conduction mode and drive single or multiple
series connected LED efficiently from a voltage
source higher than the total LED chain voltage. It
operates with a wide input voltage from 6V to 60V
and provides an externally adjustable output
current.
The PT4121E includes a high-side output
current sense circuit, which uses an external
resistor to set the nominal average output current,
and a dedicated DIM input accepts either a DC
voltage or PWM dimming.
The PT4121E is available in SOT23-6 or SOP-8
packages.
FEATURES
Simple low parts count
Wide input voltage range: 6V to 60V
High efficiency (up to 97%)
Single pin on/off and brightness control using
DC Voltage or PWM
Up to 1MHz switching frequency
Adjustable Constant LED Current
Typical 3% output current accuracy
High-Side Current Sense
Hysteretic Control: No need compensation
Inherent R
CS
open protection
Inherent open-circuit LED protection
Inherent short-circuit LED protection
Over Temperature Protection
APPLICATIONS
Low voltage halogen replacement LEDs
Automotive/Decorative lighting
Low voltage industrial lighting
LED back-up lighting
Signs/Emergency lighting
SELV lighting
LCD TV backlighting
ORDERING INFORMATION
PACKAGE
SOT23-6
SOP-8
TEMPERATURE
RANGE
-40 C to 125 C
-40℃ to 125℃
o
o
ORDERING PART
NUMBER
PT4121EE23F
PT4121EESOH
TRANSPORT
MEDIA
Tape and Reel
3000 units
Tape and Reel
4000 units
MARKING
4121E
PT4121E
xxxxxX
TYPICAL APPLICATION CIRCUIT
D1
VIN
6.0V~50V
C
IN
Rcs
VIN
VCC
DIM
GND
CSN
PT4121E
DRV
L1
CR POWTECH (SHANGHAI) CO., LTD.
PT4121E_DS_Rev EN 1.1
WWW.CRPOWTECH.COM
Page 1
PT4121E
60V Step-down High Brightness
LED Controller
PIN ASSIGNMENT
NC
1
8
NC
CSN
VIN
DIM
VIN
CSN
DIM
1
6
VCC
VCC
2
3
4
PT4121E
4121E
SOT23-6
7
6
5
2
3
5
4
DRV
DRV
GND
GND
SOP-8
PIN DESCRIPTIONS
PIN No.
SOP-8
1
2
3
4
5
6
7
8
6
5
4
3
1
2
PIN No.
SOT23-6
PIN
NAMES
NC
VCC
DRV
GND
DIM
VIN
CSN
NC
Not connected.
Internal Regulator Output. Connect a 1µF decoupling cap from this
pin to ground.
Gate-Driver Output. Connect this pin to the gate of the external
MOSFET.
Signal and power ground. Connect directly to ground plane.
Logic level dimming input. Drive DIM low to turn off the current
regulator. Drive DIM high to enable the current regulator.
Input Supply Pin. Connect a decoupling capacitor from VIN pin to
GND.
LED Current Sense Input. Connect a current-sense resistor that
programs LED average current to the VIN pin.
Not connected.
(note1)
DESCRIPTION
ABSOLUTE MAXIMUM RATINGS
SYMBOL
PARAMETER
VALUE
UNIT
V
IN
CSN
V
I/O
θ
JA
T
J
T
OP
T
STG
Supply Voltage
Current sense input (Respect to VIN)
Other I/O PIN Input Voltage
SOT23-6 Thermal Resistance
SOP-8 Thermal Resistance
Junction Temperature
Operating Temperature Range
Storage Temperature Range
ESD Susceptibility
(Note 2)
-0.3~60
+0.3~(-6.0)
-0.3~6
220
145
150
-40~125
-55 to 150
2
o
o
V
V
V
C /W
C /W
o
o
o
C
C
C
kV
Note 1:
Exceeding these Absolute Maximum Ratings may damage the device. Recommended Operating
Range indicates conditions for which the device is functional. Electrical Characteristics state DC and AC
electrical specifications under particular test conditions which guarantee specific performance limits. This
assumes that the device is within the Operating Range. Specifications are not guaranteed for parameters
where no limit is given, however, the typical value is a good indication of device performance.
Note 2:
Human body model, 100pF discharged through a 1.5kΩ resistor.
CR POWTECH (SHANGHAI) CO., LTD.
PT4121E_DS_Rev EN 1.1
WWW.CRPOWTECH.COM
Page 2
PT4121E
60V Step-down High Brightness
LED Controller
ELECTRICAL CHARACTERISTICS
(Note 3)
The following specifications apply for V
IN
=24V, T
A
=25 C, unless specified otherwise.
SYMBOL
V
IN
VCC
V
UVLO_HYS
F
SW
V
CSN
V
CSN_HYS
I
CSN
I
SD
I
OFF
DIM Input
V
DIM
V
DIM_H
V
DIM_L
V
DIM_HYS
R
DIM
I
DIM_H
I
DIM_L
Driver
R_source
R_sink
V
OH
V
OL
T
ON_MIN
T
OFF_MIN
Gate driver source resistor
Gate driver sink resistor
Gate driver output-voltage high
Gate driver output-voltage low
Minimum on time
Minimun off time
Thermal Regulation
Temperature
Thermal Shutdown Temperature
I
DRV
=10mA
I
DRV
=10mA
Guarantee by
Designer
100
100
V
GS
=5.0V
6
2
4.8
0.5
Ω
Ω
V
V
nS
nS
Internal supply voltage
DIM input voltage High
DIM input voltage Low
DIM input voltage hysterisis
DIM pull up resistor to Internal
supply voltage
DIM input leakage high
DIM input leakage low
V
DIM
=5V
V
DIM
= 0
20
50
200
2.8
22
DIM floating
2.5
0.3
80
V
mV
KΩ
µA
µA
4.2
V
ITEMS
Input Voltage
Internal Regulated Voltage
UVLO hysterisis
Max. Switching Frequency
Current sense threshold voltage
Sense threshold hysteresis
CSN Pin input current
Shutdown supply current
Quiescent supply current with
output off
No switching
V
IN
-V
CSN
=50mV
V
IN
-V
CSN
Nominal
194
VCC falling
CONDITIONS
Min.
6
4.5
5.0
0.3
1
200
±15
8
60
0.16
100
0.3
206
Typ.
Max.
60
5.5
UNIT
V
V
V
MHz
mV
%
µA
µA
mA
o
Current Sense
Operating Current
Output Switch
Thermal Shutdown
T
REG
T
SD
Note 3:
140
150
℃
℃
Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
CR POWTECH (SHANGHAI) CO., LTD.
PT4121E_DS_Rev EN 1.1
WWW.CRPOWTECH.COM
Page 3
PT4121E
60V Step-down High Brightness
LED Controller
SIMPLIFIED BLOCK DIAGRAM
VIN
REGULATOR
VCC
CS
Thermal
Derating
REFERENCE
CURRENT
SENSE COMPARATOR
GATE
DRIVER
DRV
UVLO
COMPARATOR
GND
DIM
DIM
BUFFER
OPERATION DESCRIPTION
The PT4121E in conjunction with current
sense resistor (R
CS
),the inductor (L1), and
MOSFET
forms
a
self
oscillating
continuous-mode buck converter.
When input voltage VIN is first applied, the
initial current in L1 and R
CS
is zero and there is
no output from the current sense circuit. Under
this condition, the output of CS comparator is
high. This turns on switch, causing current to flow
from V
IN
to ground, via R
CS
, the LED(s),L1 and
external MOSFET. The current rises at a rate
determined by V
IN
and L1 to produce a voltage
ramp (VCSN) across R
CS
. When (VIN-VCSN) >
230mV, the output of CS comparator switches
low and the switch turns off. The current flowing
on the R
CS
decreases at another rate. When
(VIN-VCSN) < 170mV, the switch turns on again
and the mean current on the LED is determined
by 200mV/R
CS
.
The high-side current-sensing scheme and
on-board current-setting circuitry minimize the
number of external components while delivering
LED current with ±3% accuracy, using a 1%
CR POWTECH (SHANGHAI) CO., LTD.
PT4121E_DS_Rev EN 1.1
WWW.CRPOWTECH.COM
Page 4
sense resistor. The PT4121E allows dimming
with a PWM signal at the DIM input. A logic level
below 0.3V at DIM forces PT4121E to turn off the
LED and the logic level at DIM must be at least
2.5V to turn on the full LED current. The
frequency of PWM dimming ranges from 100Hz
to 20 kHz.
The DIM pin can be driven by an external DC
voltage (V
DIM
) to adjust the output current to a
value below the nominal average value defined
by R
CS
. The DC voltage is valid from 0.5V to 2.5V.
When the DC voltage is higher than 2.5V, the
output current keeps constant.
Additionally, to ensure the reliability, the
PT4121E is built with an over temperature
protection. If the junction temperature exceeds
T
REG
, the device will reduce output current to
avoid system cause to damage.
PT4121E
60V Step-down High Brightness
LED Controller
TYPICAL PERFORMANCE CHARACTERASTICS
V
IN
=24V,3LEDs,I
OUT
=1A,T
A
=25℃，unless otherwise noted.
Efficiency
Steady State
2µS/div
Input Power On
Input Power Off
2mS/div
EN Power On
100mS/div
EN Power Off
400µS/div
200µS/div
CR POWTECH (SHANGHAI) CO., LTD.
PT4121E_DS_Rev EN 1.1
WWW.CRPOWTECH.COM
Page 5
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