EC5116

E-CMOS Corp. (www.ecmos.com.tw)

7I26N-Rev. F001

3A, 40V Asynchronous Step-Down Converter

8/12

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.

Normallyapplication 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.