EC5116|3A, 40V Asynchronous Step-Down Converter


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​​  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ 3A, ​​ 40V ​​ Asynchronous Step-Down ​​ Converter

EC5116

 

 

 

 

General Description

The EC5116 ​​ is ​​ a ​​ current ​​ mode ​​ monolithic ​​ buck switching regulator. Operating with an input range of 4.5-40V,

the EC5116 delivers 3A of continuous output current with an integrated high side N-Channel MOSFET. At light

loads, EC5116 operates in low frequency to maintain high efficiency ​​ and ​​ low ​​ output ​​ voltage ​​ ripple. ​​ Current

mode control provides tight load transient response and cycle-by-cycle current limiting.

The EC5116 guarantees robustness with input under-voltage lockout, start-up current run-away protection, output

short protection, feedback short protection and thermal protection. The EC5116 is available in 8-pin SOP package,

which provides ​​ a ​​ compact ​​ solution ​​ with ​​ minimal external components.

 

Features

4.5V to 40V operating input range

3A output current

Up to 94% efficiency

High efficiency (>78%) at light load

Internal Soft-Start

Adjustable switch frequency

Input under-voltage lockout

Start-up current run-away protection

Output short protection

Feedback short protection

Thermal protection

Available in SOP8 and ESOP8 package

 

Applications

Distributed Power Systems

Networking Systems

FPGA, DSP, ASIC Power Supplies

Green Electronics/ Appliances

 

Typical application

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ordering/Marking Information

 

EC5116 ​​ XX ​​ X ​​ X

 

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ R:Tape & Reel

Package Type:  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ ​​ F:Pb Free

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ MHESOP8  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​  ​​ ​​ ​​ ​​ ​​​​ G:Green

 ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ M1 SOP8

Device

Marking

Package

Information

EC5116MHXR

EC5116

LLLLL

YYWW

ESOP8

YY: Year code

WW: Week code

LLLLL: Lot no.

EC5116M1XR

EC5116

LLLLL

YYWW

SOP8

 

 

 

 

 

 

 

 

Pin Configurations

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Absolute Maximum Ratings

VIN, EN, SW Pin..............................................................................................................  -0.3Vto 45V

BST Pin............................................................................................................................  SW-0.3V to SW+5V

All other pins.....................................................................................................................  -0.3V to 6V

Junction Temperature2) 3) ............................................................................................... 150ºC

Lead Temperature............................................................................................................. 260ºC

Storage Temperature ........................................................................................................  -65ºC to +150ºC

 

Recommended Operating Conditions

Input Voltage VIN .............................................................................................................. 4.6Vto 40V

Output voltage Vout ...........................................................................................................  0.8Vto 37V

Operating Junction Temp......................................................................................... -40ºCto 125ºC

Thermal Performance

SOP8 ..................................................................................................................................  96....45ºC/W

ESOP8 ................................................................................................................................  50....10ºC/W

 

 

 

Note

  • Exceeding these ratings may damage the device.

  • The EC5116 guarantees robust performance from -40°C to 150°C junction temperature. The junction

temperature range specification is assured by design, characterization and correlation with statistical process

controls.

  • The EC5116 ​​ includes ​​ thermal ​​ protection ​​ that ​​ is ​​ intended ​​ to ​​ protect ​​ the ​​ device ​​ in ​​ overload ​​ conditions. ​​ Thermal protection ​​ is ​​ active ​​ when ​​ junction ​​ temperature ​​ exceeds ​​ the ​​ maximum ​​ operating ​​ junction ​​ temperature. Continuous operation over the specified absolute maximum operating junction temperature may damage the device.

4)  ​​​​ Measured on JESD51-7, 4-layer PCB.

 

Electrical Characteristics

 

VIN = 12V, TA = 25ºC, unless otherwise stated.

Item

Symbol

Condition

Min.

Typ.

Max.

Units

VIN Under-voltage  Lockout

Threshold

VIN_MIN

VIN falling

3.6

3.8

4

V

VIN Under-voltage  Lockout

Hysteresis

VIN_MIN_HYST

VIN rising

200

400

600

mV

Shutdown Supply Current

ISD

VEN=0V

 

1.6

3

µA

Supply Current

IQ

VEN=5V, VFB=1V

30

65

90

µA

Feedback Voltage

VFB

3.6V<VVIN<40V

0.784

0.8

0.816

V

Top Switch Resistance5)

RDS(ON)T

 

 

63

78

m

Top Switch Leakage Current

ILEAK_TOP

VIN=40V, VEN=0V, VSW=0V

 

 

0.1

uA

Top Switch Current Limit5)

ILIM_TOP

Minimum Duty Cycle

3.6

4.5

 

A

Switch Frequency

FSW

RRT = 330k

100

160

220

kHz

Minimum On Time5)

TON_MIN

 

 

117

 

ns

Minimum Off Time

TOFF_MIN

VFB=0V

100

150

200

ns

EN Shutdown Threshold

VEN_TH

VEN falling, FB=1V

1

1.2

1.4

V

EN shut down hysteresis

VEN_HYST

VEN rising, FB=1V

50

100

150

mV

Thermal Shutdown5)

TTSD

 

 

137

 

°C

Thermal Shutdown Recovery

Hysteresis5)

TTSDR

 

 

13

 

°C

 

Note:

5)  ​​​​ Guaranteed by design.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pin Description

PIN

SOP8

Name

Description

1

SW

SW  is the switching node that supplies power to the output. Connect the output LC filter from

SW to the output load.

2

EN

Drive EN pin high to turn on the regulator and low to turn off the regulator.

3

COMP

Compensation pin. Comp is used to compensate the regulation control loop. Connect a series

RC network from COMP to GND to compensate the regulation control loop. One ceramic cap

such as several tens pF is usually connected from COMP to GND to decouple the voltage noise.

4

FB

Output feedback pin. FB senses the output voltage and is regulated by the control loop to FB

reference voltage 0.8V. Connect a resistive divider at FB.

5

GND

Ground.

6

RT

Voltage at the RT pin is regulated at 1.2V. Switch frequency of the regulator can be adjusted by

connecting a resistor at the RT pin to ground.

7

VIN

Input voltage pin. VINsupplies power to the IC. Connect a 3.8V to 40V supply to VIN and

bypass VIN to GND with a suitably large capacitor to eliminate noise on the input pin to the IC.

8

BST

Bootstrap pin for top switch. A 0.1uF or larger capacitor should be connected between this pin

and SW pin to supply current to the top switch and top switch driver.

 

Block Diagram

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Performance Characteristics

Vin=12V, Vo=5V, L=22uH, Cout=47uF, Cin=20uF, Ta=25°C unless otherwise noted.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Functional Description

The EC5116 is an asynchronous, current-mode, step-down regulator. ​​ It regulates input voltages from 3.8V to 40V down to an

output voltage as low as 0.8V, and ​​ is ​​ capable of supplying up to 3A of load current.

 

Current-Mode Control

The EC5116 utilizes current-mode control to regulate the output voltage. The output voltage is measured at the FB pin through

a resistive divider and the error is amplified by the internal transconductance error amplifier. The output of internal error

amplifier is compared to the switch current measured internally to control the output current limit.

 

PFM Mode

The EC5116 operates in PFM mode at light load. In PFM mode, switch frequency is continuously controlled in proportion to

the load current, i.e. switch  frequency is decreased when load current ​​ drops to boost power efficiency at light load by reducing

switch-loss, while switch frequency is increased when load current rises, minimizing both load current and output voltage

ripples.

 

Power Switch

An N-Channel MOSFET switch is integrated on the EC5116 to down convert the input voltage to the regulated output voltage.

Since the top MOSFET needs a gate voltage great than the input voltage, a boost capacitor connected between BST and SW

pins is required to drive the gate of the top switch. The boost capacitor is charged by the internal 3.3V rail when SW is low.

 

VIN Under-Voltage Protection

EC5116 can regulate a wide range input voltage down to an output voltage. If the input voltage decreases to under voltage

lockout threshold, the regulator enters into UVLO protection to shutdown internal logic and function blocks.

 

Enable Pin

EN pin is a digital control pin that turns the regulator on and off. Drive EN pin high to turn on the regulator and drive it low to

turn it off. ​​ A resistor such as 100K can be connected between EN pin and VIN pin for automatic startup.

 

COMP Voltage

The current limit is decided by the maximum comp voltage which is around 2.5V. Comp voltage is also adjusted with the output

current. The comp voltage decreases as load current drop. When comp voltage keeps the maximum value for around 12480

cycle, the over load protection is triggered. IC enters into the hiccup mode during the OLP.

 

Output Current Run-Away Protection

At start-up, due to the high voltage at input and low voltage at output, current inertia of output inductance ​​ can ​​ be ​​ easily built

up, resulting in a large start-up output current. COMP value is limited ​​ and ​​ rise ​​ up ​​ slowly ​​ for ​​ a ​​ period ​​ of ​​ time when start up.

By such ​​ control ​​ mechanism, ​​ the output current at start-up is well controlled.

 

Output Short Protection

When the output is shorted to ground, output current rapidly rises and if it hits the OCP (over current protection) limit, which is

1.3A above the normal peak current limit, switch frequency is halved to allow time for the inductor current to fall to a safe level.

If the OCP limit is hit again in the next cycle, switch frequency is halved again. In the extreme case, switch frequency can be

decreased to 1/128 of the original frequency set by the resistor at the RT pin.

 

Feedback Short Protection

If the FB pin is detected to be short to ground for more than 15 switch cycles, the EC5116 is latched off. The regulator can be

Reactivated again through recycling Vin or EN voltage.

 

Thermal Protection

When ​​ EC5116 ​​ inner ​​ temperature ​​ rises ​​ above ​​ the Over Temperature Protection threshold, it is forced into thermal shut-

down. ​​ Only ​​ when IC inner temperature drops below Over Temperature Recovery threshold can the regulator becomes active

again.

 

 

 

 

 

 

 

 

Application Information

Setting the Output Voltage

The output ​​ voltage is set using a resistive divider from the output voltage to FB pin as Figure ​​ 1. The voltage divider divides

the output voltage down to the feedback voltage by the ratio:

 

 

 

 

 

 

 

 

 

 

 

 

Where ​​ VFB ​​ is ​​ the ​​ feedback ​​ voltage ​​ and ​​ VOUT ​​ is the output voltage. The output voltage is:

 

 

VFB is 0.8V reference. R2 can be as high as 100K, but a typical value is 10K~20K.For example,R2 is 22K,R5 is determined by:

 

 

One ​​ ceramic ​​ cap ​​ (C5) ​​ such ​​ as ​​ 100nF/6.3V ​​ is suggested ​​ to parallel with R2 to decouple noise voltage for feedback loop

stability in some practical application.

 

Operating Frequency

EC5116 working frequency can be adjusted in different application. Set the resistor connected to RT pin to setup the working

frequency as Figure 2 and following expression.

 

 

 

 

 

 

 

 

 

 

EN Function

EN ​​ pin ​​ is ​​ a ​​ digital ​​ input ​​ that ​​ turns ​​ the ​​ regulator ON or OFF. Drive EN ​​ pin ​​ high ​​ to ​​ turn ​​ on ​​ the regulator and drive it low

to turn off regulator. Usually, pull up with 100K ​​ (R1) resistor for automatic startup (R6=NC). Low input voltage protection can

be setup through EN pin to adjust the R1and R6 as Figure ​​ 3. EN pin voltage below 1.2V to turn off EC5116 when low input

voltage.

 

 

 

 

 

 

 

 

 

 

 

For ​​ example, ​​ Vin=12V, ​​ setup ​​ the ​​ Vin=10V ​​ to trigger the low input voltage protection. So, R1 and R6 can be configured as

R1=1M and R6=136.3K.

 

BST Capacitor

BST cap supplies the drive for the high-side N-MOSFE switch, connected from the BST pin to SW pin as Figure 4.

 

 

 

 

 

 

 

 

 

The BST cap is charged by the internal 3.3V rail when SW is low. Usually, one ceramic cap 0.1uF or greater capacitor is ok for

high side MOS driver.

 

Compensation Loop

COMP is used to compensate the regulation control loop for system stability and transient response. Connect a series RC

Network (Pole-zero combination) from COMP to GND to optimize the control loop as Figure 5.

 

 

 

 

 

 

 

 

 

 

In ​​ some ​​ cases, ​​ an ​​ additional ​​ ceramic ​​ capacitor (C6 such as 47pF) from COMP to GND is required ​​ to eliminate ​​ the ​​ high

frequency ​​ noise influence.

Normally application with 5V/3.3V output, 12V/24V input, the below table parameter is recommended.

 

 

 

Power Inductor

The inductor is required to supply constant current to the output load. A  larger value inductor results in less current ripple and

Also lower output ripple. However, the larger value inductor has a larger physical size, bigger series resistance, high cost or

lower saturation current. A good rule to determining the inductance is to allow the peak-to-peak ripple current in the inductor.

It’s recommended to allow inductor ripple current IPP of 30% maximum peak current. So we can get the proper inductor value

as follow.

 

 

 

Where ​​ VOUT is output voltage, VIN is input voltage, fS is switching frequency and IPP is the peak-to-peak inductor ripple

current. Choose an inductor that will not be saturate under the maximum inductor peak current. The peak inductor current can

be calculated by following expression:

 

 

 

Where IOUT is the load current.

 

 

 

 

 

Freewheel Diode

Freewheel ​​ diode supply the ​​ current ​​ route ​​ when high ​​ side ​​ MOS ​​ turns ​​ off. ​​ The ​​ system ​​ efficiency is worse if ​​ the forward

voltage drop is high. So, this ​​ diode ​​ is ​​ recommended ​​ to ​​ use ​​ the ​​ schottky diode ​​ with lower ​​ forward voltage drop to improve

overall efficiency. For example, the B540 (5A/40V) schottky diode performs well in application.

 

Input Capacitor

Use low ESR capacitors for the best performance. Ceramic capacitors are preferred, but ​​ tantalum ​​ or ​​ low-ESR ​​ electrolytic

Capacitors may also suffice. It’s recommended to choose X5R or X7R dielectrics ​​ when ​​ using ​​ ceramic ​​ capacitors.

The RMS current in the input capacitor can be estimated by following expression:

 

 

 

Choose the input capacitor whose RMS current rating greater than ICinput. Input ​​ voltage ​​ ripple for low ESR capacitors can be

estimated as follow:

 

 

 

It should increase the input capacitor if the input voltage ripple is big. Besides, one ceramic cap such as 0.1uF is suggested to

be placed as close to the IC as possible.

 

Output Capacitor

The output capacitor is required to maintain the DC output voltage. The output voltage ripple can be estimated by following.

 

 

 

Where COUT is the output capacitance value and RESR is the equivalent series resistance (ESR) value of the output capacitor.

Ceramic, tantalum, or low ESR electrolytic capacitors are recommended. Low ESR capacitors are preferred to keep the output

 

Pcb Layout

PCB ​​ layout ​​ is ​​ very ​​ important ​​ to ​​ achieve ​​ stable operation. It is highly recommended to duplicate EVB layout as follow these

guidelines.

  • Keep ​​ the ​​ path ​​ of ​​ switching ​​ current ​​ short ​​ and minimize ​​ the ​​ loop ​​ area ​​ formed ​​ by ​​ input ​​ cap, high-side MOSFET and

freewheel diode.

  • Bypass ​​ ceramic ​​ capacitors ​​ are ​​ suggested ​​ to be put close to the Vin Pin.

  • Ensure all feedback connections are short and direct. Place the feedback resistors and compensation components as

close to the chip as possible.

  • Route SW away from sensitive analog areas such as FB.

  • Connect IN, SW, and especially GND respectively to a large copper area to cool the chip to improve thermal performance

and long-term reliability. The 2os copper thickness is suggested for better thermal performance in real application. Figure

6 is the PCB layout reference.