MIC26903ZA_14 Datasheet, PDF (3/29 Pages) Micrel Semiconductor – 28V, 9A Hyper Speed Control Synchronous DC/DC Buck Regulator

Micrel, Inc.
MIC26903-ZA
Pin Description (Continued)
Pin Number
22
23
24
25
26
27
28
Pin Name
CS
SGND
FB
PG
EN
VIN
VDD
Pin Function
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. 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.
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).
Feedback input: Input to the transconductance amplifier of the control loop. The FB pin is regulated to
0.6V. A resistor divider connecting the feedback to the output is used to adjust the desired output
voltage.
Power Good output: Open drain output. The PG pin is externally tied with a resistor to VDD. A high
output is asserted when VOUT > 92% of nominal.
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, the supply current of the device is greatly reduced (typically
5µA). Do not leave the EN pin open.
Power Supply Voltage input: Requires a bypass capacitor to SGND.
5V Internal Linear Regulator output: VDD supply is the power MOSFET gate drive supply voltage and
the supply bus for the IC. VDD is created by internal LDO from VIN. When VIN < +5.5V, VDD should
be tied to PVIN pins. A 1µF ceramic capacitor from the VDD pin to SGND pins must be placed next to
the IC.
July 22, 2014
3
Revision 1.1