PWM/PFM Automatic Controlled DC-DC Converters
—Backlight Driver
ECL2401
General Description
ECL2401 series is a group of high efficiency synchronous-rectification type buck regulator using a constant frequency,
current mode architecture. Automatic PWM/PFM mode operation increases efficiency and decreases output voltage
ripple at light loads, further extending battery life. Switching frequency is internally set at 1.4MHz, allowing the use of
small surface mount inductors and capacitors. 100% duty cycle provides low dropout operation.
Features
◆Output Current : 800mA
◆Shutdown Current : <1µA
◆Oscillation Frequency : 1.4MHz
Applications
◆LED driver
Typical Application Circuit
Note: ILED=100mV/RSET
Functional Pin Description
Pin Number | Pin Name | Function |
1 | CE | Chip Enable Pin |
2 | GND | Common Ground |
3 | LX | Switching Output |
4 | VIN | Power Input |
5 | FB | Feedback Voltage Pin |
Ordering Information
ECL2401 N XX N
Embossed Tape :
R：Standard Feed
S：Reverse Feed
Package Type：
B2：SOT23-5L
A：VFB=0.1V
For example:
ECL2401AB2R is defined as ECL2401, the feedback voltage is 0.1V, the oscillator frequency of 1.4MHz, Package
SOT23-5L, Reverse Feed.
Marking Information
 | Designator | Symbol | Information | |
product name | ① | 3 | ECL2401 | |
feedback voltage | ② | A | VFB=0.1V | |
product package type | ③ | M | SOT23-5L | |
assembly lot No. | ④ |
| 0-9，A-Z; 0-9，A-Z mirror writing，repeated（G，I，J，O，Q，W exception） | |
Pin Configuration
Function Block Diagram
Absolute Maximum Ratings
Parameter | Symbol | Ratings | Units | |
Input Supply Voltage | VIN | -0.3～6.5 | V | |
Output Voltage | VOUT | -0.3～6.5 | ||
VLX | -0.3～VIN + 0.3 | |||
CE Voltage | VCE | -0.3～VIN + 0.3 | V | |
Peak LX Current | ILX | 1200 | mA | |
Power Dissipation | SOT23-5L | Pd | 250 | mW |
Operating Temperature Range | Topr | -40～＋85 | ℃ | |
Storage Temperature Range | Tstg | -55～＋125 | ||
Note: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
Electrical Characteristics VIN=5V, L=2.2uH(Ta=25℃, unless otherwise noted)
Parameter | Symbol | Conditions | Min | Type | Max | Units |
Feedback Voltage | VFB | - | 0.09 | 0.1 | 0.11 | V |
Input Voltage Range | VIN | - | 2 | - | 6 | |
Line regulation | △VOUT | ILED=300mA | - | 0.45 | - | % |
Efficiency | EFFI | ILED=200mA | － | 92 | － | % |
CE ”Low” voltage | VCEL | - | - | - | 0.9 | V |
CE ”High” voltage | VCEH | - | 1.1 | - | - | V |
Shutdown Current | ISHDN | VCE=0V | - | - | 1 | µA |
Quiescent Current | IDD | VFB=0.1V*0.9 | － | 300 | - | µA |
Switch Current Limit | ILIM | - | - | 1200 | - | mA |
PFM switching point | IPFM | VIN=5V |
| 100 |
| mA |
Oscillation Frequency | FOSC | ILED=500mA | - | 1.4 | - | MHz |
Max Duty Circle | MAXDTY | - | 100 | - | - | % |
Thermal Shutdown | TSD | - | - | 150 | - | ℃ |
Thermal Hysteresis | THYST | - | - | 20 | - | ℃ |
Typical Application
Figure 1 Typical application circuit
Note: ILED=100mV/RSET
Figure 2 Typical application circuits with PWM dimming signal
Calculate ILED using the following equations
Where VPWM is the amplitude of PWM signal.
For example, for 3.3V VPWM, R1=4.7K, R2=100K, R3=47K.
The value of C3 depends on the frequency of PWM dimming; an empirical suggestion is around 0.1uF for MHz and 10uF for low frequency under KHz.
Typical Performance Characteristics
