EC3202S|2A, 1.5MHz, Syn.Step Down DC/DC Converter


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2A, 1.5MHz, Synchronous

Step Down DC/DC Converter

 

 

EC3202S

 

 

General Description

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.

.

Features

  • 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

 

Applications

 

  • Cellular phones

  • PDAs and smart phones

  • MP3 players

  • Digital still cameras

  • Slim-type DVD

  • Wireless and DSL card

  • Microprocessors and DSP core supplies

  • Portable instruments

 

Pin Assignments

 

Pin Description

TSOT23-5L

TDFN 2x2-6L

Symbol

Description

1

2

EN

Enable control input pin.

2

5

GND

Ground pin.

3

4

SW

Power switch output.

4

3

Vin

Main supply pin.

---

1

NC

No connected.

5

6

FB

Feedback pin.

Vout=0.6×(1+R1/R2).

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.

Ordering Information

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part Number

Package

Marking

Marking Information

EC3202SNT2R

TSOT23-5L

07LDD

or

08LDD

  • L:The last number of Lot No

  • DD:Date Code

  • 07or 08:Tracking code

 

 

 

 

 

 

Marking Information:

A: Tracking Code +B: Lot Number +C:Date code

 

Tracking code 08:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tracking code 07

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absolute Maximum Ratings

(Note 1)

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

(Note 2)

TSOT23-5L:

Thermal Resistance, θJA …………..………………… 250°C/W

Thermal Resistance, θJC …………..………………… 130°C/W

TDFN 2x2-6L:

Thermal Resistance, θJA …………..…………………. 120°C/W

Thermal Resistance, θJC …………..…………………… 20°C/W

 

Recommended Operating Conditions

(Note 3)

Supply Input Voltage ……….………………… +2.5V to +5.5V

Junction Temperature Range…………… –40°C to +125°C

Ambient Temperature Range …………… –40°C to +85°C

 

Block Diagram

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Electrical Characteristics

(Vin = 5V, Vout= 1.8V, L = 2.2uH, Cout = 10uF, TA = 25°C, unless otherwise specified)

PARAMETER

Symbol

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Supply Voltage

Vin

 

2.5

 

5.5

V

Output Voltage Line Regulation

Vout

Vin = 2.5V to 5.5V

3

 

3

%V

Output Voltage Load Regulation

VLR

 

3

 

3

%

Reference Voltage

VREF

For adjustable Vout

0.588

0.6

0.612

V

Output Range (Adjustable Voltage)

Vout

Vin = 2.5V to 5.5V

3

 

+3

%

Shutdown Current

IS
VEN = 0V

 

0.1

1

µA

Quiescent Current

IQ
VEN = Vin,
VFB = VREF × 1.1
No Switching

 

100

 

µA

SW Leakage Current

ILEAK
VEN = 0V,
VSW = 0V or Vin

−1

 

1

µA

PMOSFET On Resistance*

RDSONP
ISW = 100mA

 

110

 

mΩ

NMOSFET On Resistance*

RDSONN
ISW = 100mA

 

95

 

mΩ

PMOSFET Current Limit*

ILIM
Duty cycle = 100%
Current Pulse Width < 1ms

 

3

 

A

Oscillator Frequency

FOSC
 

1.2

1.5

1.8

MHz

Thermal Shutdown Threshold*

TS
 

 

160

 

°C

EN High Level Input Voltage

VENH
40°C ≤ TA ≤ 85°C

1.5

 

 

V

EN Low Level Input Voltage

VENL
40°C ≤ TA ≤ 85°C

 

 

0.4

V

EN Input Current

IEN
VEN = 0V to Vin

−1

 

1

µA

 

* 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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Characteristics

 

 

Startup

(Vin=5.0V, Vout=1.8V,Iload=2A)

 

Shutdown

(Vin=5.0V, Vout=1.8V,Iload=2A)

Vin

5V/div

 

 

Vout

1V/div

 

IL

1A/div

50us/div

Vin

5V/div

 

Vout

1V/div

 

IL

1A/div

10us/div

 

Output Ripple

(Vin=5.0V, Vout=1.8V,Iload=2A)

 

Load Transient

(Vin=5.0V, Vout=1.8V,Iload=0.2A~2A)

 

 

Vout(AC)

10mv/div

 

IL

1A/div

500ns/div

 

 

 

Vout(AC)

50mv/div

 

IL

2A/div

200us/div

 

Soft Start

Iload=2A

 

Short Protection/Current limit

(Vin=5.0V, Vout=1.8V,open to short)

 

 

 

Vout

1V/div

 

IL

1A/div

20us/div

 

 

Vout

1V/div

 

IL

1A/div

200us/div

 

 

 

 

 

 

 

 

 

FUNCTIONAL DESCRIPTION

Overview

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.

 

Dropout Operation

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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

APPLICATION INFORMATION

Inductor Selection

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

 

Capacitor Selection

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).

 

 

Package Information

TSOT23-5L

 

 

 

 

 

 

 

 

 

 

A

C

D

B

A1

H

L

e

b

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symbol

Dimensions in mm

Dimensions in Inch

Min

Max

Min

Max

A

0.700

1.100

0.028

0.043

A1

0.000

0.130

0.000

0.005

B

1.500

1.700

0.059

0.067

b

0.300

0.559

0.012

0.022

C

2.500

3.100

0.098

0.122

D

2.800

3.100

0.110

0.122

e

0.950 BSC

0.037 BSC

H

0.080

0.200

0.003

0.008

L

0.200

0.800

0.008

0.031

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Package Information

TDFN 2x2-6L

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

2

SEE DETAIL A

DETAIL A

 ​​ ​​ ​​​​ D

E

D2

E2

L

e

b

A

A1

A3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SYMBOLS

 

DIMENSION (MM)

 

DIMENSION (INCH)

 

MIN

NOM

MAX

 

MIN

NOM

MAX

A

 

0.700

---

0.800

 

0.028

---

0.031

A1

 

0.000

---

0.050

 

0.000

---

0.002

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ A3

 

0.175

---

0.250

 

0.007

---

0.010

b

 

0.200

---

0.350

 

0.008

---

0.014

D

 

1.950

2.000

2.050

 

0.077

0.079

0.081

D2

 

1.000

---

1.450

 

0.039

---

0.057

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ E

 

1.950

2.000

2.050

 

0.077

0.079

0.081

E2

 

0.500

---

0.850

 

0.020

---

0.033

e

 

0.650

 

0.026

L

 

0.250

---

0.400

 

0.010

---

0.016

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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