Micrel, Inc.

MIC26903

July 2011

3

M9999-071311-A

Pin Description (Continued)

Pin Number

Pin Name

Pin Function

22

CS

Current Sense (Input): The CS pin senses current by monitoring the voltage across the low-side

MOSFET during the OFF-time. The current sensing is necessary for short circuit protection and zero

current cross comparator. In order to sense the current accurately, connect the low-side MOSFET

drain to SW using a Kelvin connection. The CS pin is also the high-side MOSFET’s output driver

return.

23

SGND

Signal ground. SGND must be connected directly to the ground planes. Do not route the SGND pin

to the PGND Pad on the top layer, see PCB layout guidelines for details.

24

FB

Feedback (Input): Input to the transconductance amplifier of the control loop. The FB pin is regulated

to 0.8V. A resistor divider connecting the feedback to the output is used to adjust the desired output

voltage.

25

PG

Power Good (Output): Open Drain Output. The PG pin is externally tied with a resistor to VDD. A

26

EN

Enable (Input): A logic level control of the output. The EN pin is CMOS-compatible. Logic high =

enable, logic low = shutdown. In the off state, supply current of the device is greatly reduced (typically

5µA). The EN pin should not be left open.

27

VIN

Power Supply Voltage (Input): Requires bypass capacitor to SGND.

28

VDD

5V Internal Linear Regulator (Output): VDD supply is the supply bus for the IC control circuit. VDD is

ceramic capacitor from the VDD pin to SGND pins

must be place next to the IC.