2A, 28V, Buck Converter
EC3282S
General Description
The EC3282S is a monolithic synchronous buck regulator. The device integrates 95mΩ MOSFETS
that provide 2A Continuous load current over a wide
operating input voltage of 4.5Vto 28V.Current mode control provides fast transient response and cycle-by-cycle current limit. An adjustable soft-start prevents
inrush current at turn on.
Features
2A Output Current
Wide 4.5V to 28V Operating Input Range
Output Adjustable from 0.925V to 0.8*VIN
Up to 96 Efficiency
● Programmable Soft-Start
● Stable with Low ESR Ceramic Output Capacitors
● Fixed 340KHz Frequency
● Cycle-by-Cycle Over Current Protection
● Short-Circuit Protection
● Input Under Voltage Lockout
● Package:SOP 8L
Applications
● Distributed Power Systems
● Networking Systems
● FPGA, DSP, ASIC Power Supplies
● Green Electronics/ Appliances
● Notebook Computers
Pin Configurations
2A, 28V, Buck Converter
EC3282S
Typical Applications
Ordering Information
M1= SOP 8L
Part Number | Package | Marking | Marking Information |
EC3282SNM1R | SOP 8L | 3282S LLLLL YYWWT | LLLLL is Lot Number YYWW is date code T is internal tracking code |
2A, 28V, Buck Converter
EC3282S
Function Block
Absolute Maximum Ratings
Parameter | Symbol | Value | Unit |
Supply Voltage | VIN | -0.3 to 30 | V |
SW Voltage | VSW | -0.3 toVIN+0.3 | V |
BS Voltage | VBS | VSW – 0.3V to VSW+6 | V |
EN / FB / COMP Voltage | | -0.3 to 5 | V |
Continuous SW Current |
| Internally limited | A |
Operating Junction Temperature | TJ | 150 | ºC |
Storage Temperature | TSTG | -65 to 150 | ºC |
Power Dissipation | PD | Internally limited | W |
Thermal Resistance-Junction to Ambient | θJA | 87 | ºC / W |
Note: Exceeding these limits may damage the device. Even the duration of exceeding is very short. Exposure to
absolute maximum rating conditions for long periods may affect device reliability。
2A, 28V, Buck Converter
EC3282S
Recommended Operating Conditions
Parameter | Symbol | Value | Units |
Supply Input Voltage | VIN | 4.5 to +28 | V |
Operating Junction Temperature | TJ | -20 to +125 | °C |
Electrical Characteristics
(VIN = 12V, TJ = 25℃ unless otherwise specified.)
Note: * Guaranteed by design, not tested
Parameter | Symbol | Conditions | Min | Typ | Max | Unit |
Feedback Voltage | VFB | 4.5V ≤ VIN ≤ 28V | 0.9 | 0.925 | 0.95 | V |
Feedback Overvoltage Threshold |
|
|
| 1.1 |
| V |
High-Side Switch-On Resistance* |
|
|
| 95 |
| mΩ |
Low-Side Switch-On Resistance* |
|
|
| 95 |
| mΩ |
High-Side Switch Leakage |
| VEN = VSW = 0V | , |
| 10 | uA |
Upper Switch Current Limit* |
| Min Duty Cycle | 2.7 | 3.5 |
| A |
COMP to Current Limit Trans conductance | GCOMP |
|
| 3.3 |
| A/V |
Error Amplifier Trans conductance | GEA | ΔICOMP = ±10uA |
| 920 |
| uA/V |
Error Amplifier DC Gain*A | VEA |
|
| 480 |
| V/V |
Switching Frequency | fSW |
|
| 340 |
| KHz |
Short Circuit Switching Frequency |
| VFB = 0V |
| 120 |
| KHz |
Maximum Duty Cycle | DMAX | VFB = 0.8V |
| 92 |
| % |
Minimum On Time* |
|
|
| 220 |
| nS |
EN Shutdown Threshold Voltage |
| VEN Rising | 1.1 | 1.4 | 2 | V |
EN Shutdown Threshold Voltage Hysteresis |
|
|
| 180 |
| mV |
EN Lockout Threshold Voltage |
|
| 2.2 | 2.5 | 2.7 | V |
EN Lockout Hysteresis |
|
|
| 130 |
| mV |
Supply Current in Shutdown |
| VEN = 0V |
| 0.3 | 3 | uA |
IC Supply Current in Operation |
| VEN = 3V, VFB=1.0V |
| 1.3 | 1.5 | mA |
Input UVLO Threshold Rising | UVLO | VEN Rising | 3.8 | 4.05 | 4.4 | V |
Input UVLO Threshold Hysteresis |
|
|
| 100 |
| mV |
Soft-start Current |
| VSS = 0V |
| 6 |
| uA |
Soft-start Period |
| CSS =0.1uF |
| 15 |
| mS |
Thermal Shutdown Temperature* |
| Hysteresis =25°C |
| 160 |
| ℃ |
Typical Applications
EC3282S Circuit, 3.3V/2A output
EC3282S Circuit, 3.3V/2A output with EN function
Note: C2 is required for separate EN signal.
Applications
Output Voltage Setting
Figure 1 shows the connections for setting the outputvoltage. Select the proper ratio of the two feedbackresistors
R1 and R2 based on the output voltage.Typically, use R2≈10KΩ and determine R1 from the following
equation:
Table1-Recommended Resistance Values:
Inductor Selection
The inductor maintains a continuous current to the output load. This inductor current has a ripple that is
dependent on the inductance value: higher inductance reduces the peak-to-peak ripple current. The trade off
for high inductance value is the increase in inductor core size and series resistance, and the reduction in
current handling capability. In general,L based on the ripple current requirement:
Where VIN is the input voltage, VOUT is the output voltage,fSW is the switching frequency, IOUTMAX is the
maximumoutput current, and KRIPPLE is the ripple factor. Typically,choose KRIPPLE =~ 30% to correspond to the peak-to-peak ripple current being ~30% of the maximum output current. With this inductor value,the peak inductor
current is IOUT·(1+KRIPPLE/2). Make sure that this peak inductor current is less than the upper switch current limit.
Finally, select the inductor core size so that it does not saturate at the current limit. Typical inductor values
for various output voltages are shown in Table 2.
Input Capacitor
The input capacitor needs to be carefully selected to maintain sufficiently low ripple at the supply input of the converter.
A low ESR Electrolytic (EC) capacitor is highly recommended. Since large current flows in and out of this capacitor
during switching, its ESR also affects efficiency.When EC cap is used, the input capacitance needs to be equal to
or higher than 68uF. The RMS ripple current rating needs to be higher than 50% of the output current. The input
capacitor should be placed close to the VIN and GND pins of the IC, with the shortest traces possible. The input capacitor
can be placed a little bit away if a small parallel 0.1uF ceramic capacitor is placed right next to the IC.
When Vin is >15V, pure ceramic Cin (* no EC cap) is not recommended. This is because the ESR of a ceramic cap is
often too small, Pure ceramic Cin will work with the parasite inductance of the input trace and forms a Vin
resonant tank.When Vin is hot plug in/out, this resonant tank will boost the Vin spike to a very high voltage and
damage the IC.
Output Capacitor
The output capacitor also needs to have low ESR to keep low output voltage ripple.In the case of ceramic
output capacitors,RESR is very small and does not contribute to the ripple. Therefore, a lower capacitance value
can be used for ceramic capacitors.In the case of tantalum or electrolytic capacitors,the ripple is dominated by RESR
multiplied by the ripple current. In that case, the output capacitor is chosen to have sufficiently low ESR.
For ceramic output capacitors, typically choose of about 22uF. For tantalum or electrolytic capacitors,
choose a capacitor with less than 50mΩ ESR.
Optional Schottky Diode
During the transition between high-side switch and low-side switch, the body diode of the low side power
MOSFET conducts the inductor current. The forward voltage of this body diode is high. An optional Schottky
diode may be paralleled between the SW pin and GND pin to improve overall efficiency.
Stability Compensation
Figure 2. Stability Compensation
CCOMP2 is needed only for high ESR output capacitor.
The feedback loop of the IC is stabilized by the components at the COMP pin, as shown in Figure 2. The DC loop
gain of the system is determined by the following equation:
The dominant pole P1 is due to CCOMP1:
The second pole P2 is the output pole:
The first zero Z1 is due to RCOMP and CCOMP: