The EC3292A is a high-frequency, synchronous,rectified, step-down, switch-mode converter with internal power MOSFETs.
It offers a very compact solution to achieve a 2A continuous
output current over a wide input supply range, with excellent
load and line regulation.
The EC3292A has synchronous-mode Operation for higher
efficiency over the output current-load range. Current-mode
operation provides fast transient response and eases loop
stabilization.Protection features include over-current protection
and thermal shutdown.
The EC3292A requires a minimal number of readily available,
standard external components and is available in space-saving
● 4.7V to 18V input voltage
● Output adjustable from 0.8V to 15V
● Output current up to 2A
● Integrated 160mΩ/85mΩ power MOSFET switches
● Shutdown current 3μA typical
● Efficiency up to 95%
● Fixed frequency 500KHz
● Internal soft start
● Over current protection and Hiccup
● Over temperature protection
● RoHS Compliant and 100% Lead (Pb) Free
● Distributed power systems
● Networking systems
● FPGA, DSP, ASIC power supplies
● Notebook computers
● Green electronics or appliance
Power switching output.
High-side gate drive boost input.
Note: R5 and C7 are optional.
Details please see the DVT report.
Functional Block Diagram
Absolute Maximum Ratings
Supply Voltage VIN ……………………–0.3V to +20V
Switch Node VSW ……………… –0.3V to VIN+0.3V
Boost VBOOT ………………… VSW–0.3V to VSW+6V
All Other Pins ………………………… –0.3V to +6V
Junction Temperature ………………………+150°C
Lead Temperature ………………………… +260°C
Storage Temperature Range ……–65°C to +150°C
CAUTION: Stresses above those listed in “Absolute
Maximum Ratings” may cause permanent damage to
the device. This is a stress only rating and operation of
the device at these or any other conditions above those
indicated in the operational sections of this specification
is not implied.
Recommended Operating Conditions
Supply Voltage VIN ……...…………...…….…4.7V to 18V
Output Voltage VOUT ……...…………... 0.8V to VIN–3V
Operating Temperature Range ……...…–40°C to +125°C
Package Thermal Characteristics
Thermal Resistance, θJA ………………………100°C/W
Thermal Resistance, θJC ………………………… 55°C/W
(TA = +25°C, VIN = +12V, unless otherwise noted.)
Shutdown Supply Current
VEN = 0V
VEN = 2.0V,VFB =0.85V
4.7V ≤ VIN ≤ 18V
Feedback Over-voltage Threshold
Error Amplifier Voltage Gain *
High-Side Switch-On Resistance *
Low-side Switch-On Resistance *
High-Side Switch Leakage Current
VEN = 0V, VSW = 0V,
TA = +125°C
Upper Switch Current Limit
Minimum Duty Cycle
Lower Switch Current Limit
From Drain to Source
Short Circuit Oscillation Frequency
VFB = 0V
Maximum Duty Cycle
VFB = 0.5V
Minimum On Time *
EN Falling Threshold Voltage
EN Rising Threshold Voltage
Input Under Voltage Lockout Threshold
Input Under Voltage Lockout Threshold
Thermal Shutdown *
* Guaranteed by design, not tested.
VIN = 12V, VO = 3.3V, L1 = 4.7μH, C1 = 10μF, C2 = 10μF x 2, TA = +25°C, unless otherwise noted.
Start UP & Inrush Current 12V→3.3V (Load 1A) Shut Down (Iout 1A→Shut down)
Output Ripple (12V => 3.3V, Load=2A) Output Ripple (12V => 3.3V, Load=1A)
Output Ripple (12V => 3.3V, Load=0A) Dynamic Load (Iload=0.2A_1.2A;Vout=3.3V)
Short Circuit Protection Efficiency(L=4.7uA)
The EC3292A is a synchronous rectified, current-mode,
step-down regulator. It regulates input voltages from
4.7V to 18V down to an output voltage as low as
0.8V, and supplies up to 2A of load current.
The EC3292A uses current-mode control to regulate
the output voltage. The output voltage is measured at FB through a resistive voltage divider and amplified through the internal transconductance error amplifier.
The converter uses internal N-Channel MOSFET switches
to step-down the input voltage to the regulated output
voltage. Since the high side MOSFET requires a gate voltage greater than the input voltage, a boost capacitor connected between SW and BOOT is needed to drive the high side gate. The boost capacitor is charged from the internal 5V rail when SW is low.
When the EC3292A FB pin exceeds 10% of the
nominal regulation voltage of 0.8V, the over voltage
comparator is tripped forcing the high-side switch off.
BOOT: High-Side Gate Drive Boost Input. BOOT supplies
the drive for the high-side N-Channel MOSFET switch.
Connect a 0.1μF or greater capacitor from SW to BOOT
to power the high side switch.
IN: Power Input. IN supplies the power to the IC, as well
as the step-down converter switches. Drive IN with a
4.7V to 18V power source. Bypass IN to GND with a suitably large capacitor to eliminate noise on the input
to the IC.
SW: Power Switching Output. SW is the switching node
that supplies power to the output. Connect the output
LC filter from SW to the output load. Note that a capacitor is required from SW to BOOT to power the high-side switch.
FB: Feedback Input. FB senses the output voltage to
regulate that voltage. Drive FB with a resistive voltage divider from the output voltage. The feedback threshold is 0.8V.
EN: Enable Input. EN is a digital input that turns the
regulator on or off. Drive EN high to turn on the regulator, drive it low to turn it off. Pull up with 100kΩ
resistor for automatic startup.
Setting the Output Voltage
The external resistor divider sets output voltage. The feedback resistor R1 also sets the feedback loop bandwidth through the internal compensation capacitor.
(see the typical application circuit). Choose the R1 around
10KΩ,and R2 by
Use T-type network for when Vout is low.
Figure 1：T-type network
Table 1 lists the recommended T-type resistors value for
common output voltages.
Table 1: Resistor selection for common output voltages.
The inductor is required to supply constant current to
the output load while being driven by the switched
input voltage. A larger value inductor will result in less
ripple current that will result in lower output ripple
voltage. However, the larger value inductor will have a
larger physical size, higher series resistance, and/or lower saturation current. A good rule for determining
the inductance to use is to allow the peak-to-peak ripple
current in the inductor to be approximately 30% of the
maximum switch current limit. Also, make sure that the
peak inductor current is below the maximum switch
current limit. The inductance value can be calculated by:
L = [ VOUT / (fS × ΔIL) ] × (1 − VOUT/VIN)
Where VOUT is the output voltage, VIN is the input voltage,
fS is the switching frequency, and ΔIL is the peak-to-peak
inductor ripple current.
Choose an inductor that will not saturate under the
maximum inductor peak current. The peak inductor
current can be calculated by:
ILP = ILOAD + [ VOUT / (2 × fS × L) ] × (1 − VOUT/VIN)
Where ILOAD is the load current.
The choice of which style inductor to use mainly
depends on the price vs. size requirements and any EMI
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. Table 2 lists example
Schottky diodes and their Manufacturers.
Table 2: Diode selection guide.
The input current to the step-down converter is
discontinuous, therefore a capacitor is required to
supply the AC current to the step-down converter while
maintaining the DC input voltage. Use low ESR
capacitors for the best performance. Ceramic capacitors
are preferred, but tantalum or low-ESR electrolytic
capacitors may also suffice. Choose X5R or X7R
dielectrics when using ceramic capacitors.
Since the input capacitor (C1) absorbs the input
switching current it requires an adequate ripple current
rating. The RMS current in the input capacitor can
be estimated by:
IC1 = ILOAD × [ (VOUT/VIN) × (1 − VOUT/VIN) ]1/2
The worst-case condition occurs at VIN = 2VOUT, where IC1= ILOAD/2. For simplification, choose the input capacitor whose RMS current rating greater than half of the maximum load current.
The input capacitor can be electrolytic, tantalum or
ceramic. When using electrolytic or tantalum capacitors,
a small, high quality ceramic capacitor, i.e. 0.1μF, should
be placed as close to the IC as possible. When using ceramic capacitors, make sure that they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. The input voltage ripple for low ESR capacitors can be estimated by:
ΔVIN = [ ILOAD/(C1 × fS) ] × (VOUT/VIN) × (1 − VOUT/VIN)
Where C1 is the input capacitance value.
The output capacitor is required to maintain the DC
output voltage. Ceramic, tantalum, or low ESR
electrolytic capacitors are recommended. Low ESR
capacitors are preferred to keep the output voltage
ripple low. The output voltage ripple can be estimated
ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN)
× [ RESR + 1 / (8 × fS × C2) ]
Where C2 is the output capacitance value and RESR is the
equivalent series resistance (ESR) value of the output
In the case of ceramic capacitors, the impedance at the
switching frequency is dominated by the capacitance.
The output voltage ripple is mainly caused by the capacitance. For simplification, the output voltage ripple can be estimated by:
ΔVOUT = [ VOUT/(8xfS2 xLxC2)] × (1 − VOUT/VIN)
In the case of tantalum or electrolytic capacitors, the
ESR dominates the impedance at the switching
frequency. For simplification, the output ripple can be
ΔVOUT = [ VOUT/(fS × L) ] × (1 − VOUT/VIN) × RESR
The characteristics of the output capacitor also affect
the stability of the regulation system. The EC3292A can
be optimized for a wide range of capacitance and ESR values.
External Bootstrap Diode
An external bootstrap diode may enhance the efficiency
of the regulator, the applicable conditions of external
BOOT diode are:
● VOUT = 5V or 3.3V; and
● Duty cycle is high: D = VOUT/VIN > 65%
In these cases, an external BOOT diode is recommended
from the output of the voltage regulator to BOOT pin, as
shown in Figure 2.
Figure 2: Add optional external bootstrap diode to
The recommended external BOOT diode is IN4148, and
the BOOT capacitor is 0.1 ~ 1μF.
When VIN ≤ 6V, for the purpose of promote the
efficiency, it can add an external Schottky diode
between IN and BOOT pins, as shown in Figure 2.
When VIN ≤ 6V, for the purpose of promote the
Efficiency ,it can add an external Schottky diode
between IN and BOOT pins, as shown in Figure 3.
Figure 3: Add a Schottky diode to promote efficiency
when VIN ≤ 6V.
Vout = 5.0V
Vout = 3.3V
Vout = 2.5V
Vout = 1.8V
Vout = 1.2V
Table 4: BOM selection table II
PCB Layout Guide
PCB layout is very important to achieve stable operation.
Please follow the guidelines below.
1) Keep the path of switching current short and minimize the loop area formed by Input capacitor,
high-side MOSFET and low-side MOSFET.
2) Bypass ceramic capacitors are suggested to be put close to the VIN Pin.
3) Ensure all feedback connections are short and direct.
Place the feedback resistors and compensation
components as close to the chip as possible.
4) Rout SW away from sensitive analog areas such as FB.
5) Connect IN, SW, and especially GND respectively to a
large copper area to cool the chip to improve thermal
performance and long-term reliability.
BOM of EC3292A
Please refer to the Typical Application Circuit.
Table 3: BOM selection table I.
Dimensions in mm
Dimensions in Inch