EC3202S is a high efficiency step down DC/DC converter operated with current mode and constant frequency. The internal switch and synchronous rectifier are integrated for high efficiency. External Schottky diodes are not required. The supply current is only 120µA during operation and drops to less than 1µA in shutdown. EC3202S can supply 2A of load current from 2.5V to 5.5V supply voltage.
The switching frequency is set at 1.5MHz, allowing the use of small surface mount inductors and capacitors. It can run 100% duty cycle for low dropout application. The output voltage of EC3202S is adjustable from the FB pin.
2A output current
Current mode operation
High efficiency up to 95%
Shutdown current < 1µA
2.5V to 5.5V supply voltage
Over temperature protection
Constant frequency operation
Full duty ratio, 0 – 100% in dropout
RoHS Compliant and Lead (Pb) Free
PDAs and smart phones
Digital still cameras
Wireless and DSL card
Microprocessors and DSP core supplies
Enable control input pin.
Power switch output.
Main supply pin.
Add optional C1 to speed up transient response.
Typical Application Circuit, Adjustable Output Voltage
Vout = VFB × (1 + R1/R2)
with R1 = 300k for typical application,
and C1 should be in the range between 10pF and 47pF for component selection.
A: Tracking Code ＋B: Lot Number ＋C:Date code
Tracking code 08：
Tracking code 07：
Absolute Maximum Ratings
Vin to GND …………………………………………… –0.3V to +6V
SW Voltage to GND ...…………………… –0.3V to Vin+0.3V
EN Voltage to GND ..……………………………… –0.3V to Vin
FB/Vout to GND ..………………………………… –0.3V to Vin
SW Peak Current ………………………………………….………. 3A
Operating Temperature Range ……...… –40°C to +85°C
Junction Temperature ……………..………….…........ +150°C
Storage Temperature Range …………... –65°C to +150°C
Lead Temperature (Soldering 10s) …………...…. +260°C
ESD Classification …………………………………………… Class 2
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.
Package Thermal Characteristics
Thermal Resistance, θJA …………..………………… 250°C/W
Thermal Resistance, θJC …………..………………… 130°C/W
Thermal Resistance, θJA …………..…………………. 120°C/W
Thermal Resistance, θJC …………..…………………… 20°C/W
Recommended Operating Conditions
Supply Input Voltage ……….………………… +2.5V to +5.5V
Junction Temperature Range…………… –40°C to +125°C
Ambient Temperature Range …………… –40°C to +85°C
(Vin = 5V, Vout= 1.8V, L = 2.2uH, Cout = 10uF, TA = 25°C, unless otherwise specified)
Output Voltage Line Regulation
Vin = 2.5V to 5.5V
Output Voltage Load Regulation
For adjustable Vout
Output Range (Adjustable Voltage)
Vin = 2.5V to 5.5V
VEN = 0V
VEN = Vin,
VFB = VREF × 1.1
SW Leakage Current
VEN = 0V,
VSW = 0V or Vin
PMOSFET On Resistance*
ISW = 100mA
NMOSFET On Resistance*
ISW = −100mA
PMOSFET Current Limit*
Duty cycle = 100%
Current Pulse Width < 1ms
Thermal Shutdown Threshold*
EN High Level Input Voltage
−40°C ≤ TA ≤ 85°C
EN Low Level Input Voltage
−40°C ≤ TA ≤ 85°C
EN Input Current
VEN = 0V to Vin
* Guaranteed by design not for test.
Note 1: Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may affect device reliability.
Note 2: θJA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Pin 2 of TSOT23-5 packages is the case position for θJC measurement. Measured at the exposed pad of the package.
Note 3: The device is not guaranteed to function outside its operating conditions.
Short Protection/Current limit
(Vin=5.0V, Vout=1.8V,open to short)
The EC3202S is a constant frequency current mode PWM step down converter. EC3202S is optimized for low voltage, Li-ion battery, powered applications where high efficiency and small size are critical. The device integrates both a main switch and a synchronous rectifier, which provides high efficiency and eliminates an external Schottky diode. EC3202S can achieve 100% duty cycle. The duty cycle D of a step down converter is defined as:
D = TON × FOSC × 100% ≈ × 100%
Where TON is the main switch on time, FOSC is the oscillator frequency (1.5MHz), Vout is the output voltage and Vin is the input voltage.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for superior load and line response and protection of the internal main switch and synchronous rectifier. EC3202S switches at a constant frequency (1.5MHz) and regulates the output voltage. During each cycle the PWM comparator modulates the power transferred to the load by changing the inductor peak current based on the feedback error voltage. During normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the next cycle starts or the inductor current drops to zero. The device skips pulses to improve efficiency at light load.
EC3202S allows the main switch to remain on for more than one switching cycle and increases the duty cycle while the input voltage is dropping close to the output voltage. When the duty cycle reaches 100%, the main switch is held on continuously to deliver current to the output up to the P MOSFET current limit. The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor.
Short Circuit Protection
The EC3202S has short circuit protection. When the output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the P MOSFET current limit. The frequency will return to the normal values once the short circuit condition is removed and the Vout reaches regulated voltage.
Maximum Load Current
The EC3202S can operate down to 2.5V input voltage; however the maximum load current decreases at lower input due to large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely the current limit increases as the duty cycle decreases.
A 2.2μH to 4.7μH is recommended for general used. The value of inductor depends on the operating frequency. Higher frequency allows smaller inductor and capacitor but increases internal switching loss. Two inductor parameters should be considered, current rating and DCR. The inductor with the lowest DCR is chosen for the highest efficiency.
The inductor value can be calculated as:
L ≥ [VOUT/(f × ΔIL)](1 – VOUT/VIN)
ΔIL: inductor ripple current, which is defined as:
ΔIL = VOUT[(1 – VOUT/VIN)/(L × f)] (General Setting)
≈ α × IO-MAX (α = 0.2~0.4)
The inductor should be rated for the maximum output current (IO-MAX) plus the inductor ripple current (ΔIL) to avoid saturation. The maximum inductor current (IL-MAX) is given by:
IL-MAX = IO-MAX +ΔIL/2
The small size of ceramic capacitors are ideal for EC3202S applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types, such as Y5V or Z5U. A 4.7μF input capacitor and a 10μF output capacitor are sufficient for most EC3202S applications.
When selecting an output capacitor, consider the output ripple voltage and the ripple current. The ESR of capacitor is a major factor to the output ripple. For the best performance, a low ESR output capacitor is required. The ripple voltage is given by:
ΔVO = ΔIL [ESR + 1/(8 × f × CO)]
Output Voltage Programming
(Adjustable Voltage Version)
The output voltage of EC3202S is set by the resistor divider according to the following formula:
VOUT = VFB × (1 + R1/R2)
R1 is the upper resistor of the voltage divider. For transient response reasons, a small feed-forward capacitor (CF) is required in parallel to the upper feedback resistor, and33pF is recommended.
Checking Transient Response
The regulator loop response can be checked by looking at the load transient response. Switching regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT will be shifted immediately by an amount equal to (ΔILOAD × ESR), where ESR is the effective series resistance of COUT. ΔILOAD will also begin to charge or discharge COUT, which generates a feedback error signal. Then the regulator loop will act to return VOUT to its steady state value. During this recovery time, VOUT can be monitored for overshoot or ringing that will indicate the stability problem.
The discharged bypass capacitors are effectively put in parallel with COUT, causing a rapidly drop in VOUT. No regulator can deliver enough current to prevent this problem if the load switch resistance is low and it is driven quickly. The only solution is to limit the rise time of the switch drive, so that the load rise time will be limited to approximately (25 × CLOAD).
Dimensions in mm
Dimensions in Inch
SEE DETAIL A