MIC261203 Datasheet, PDF (2/31 Pages) Micrel Semiconductor – 28V, 12A Hyper Light Load™ Synchronous DC/DC Buck Regulator

Micrel, Inc.
MIC261203
Ordering Information
Part Number
MIC261203YJL
Voltage
Adjustable
Switching Frequency
600kHz
Junction Temperature
Range
–40°C to +125°C
Package
28-Pin 5mm x 6mm MLF^®
Lead Finish
Pb-Free
Pin Configuration
28-Pin 5mm x 6mm MLF^® (YJL)
Pin Description
Pin Number Pin Name
1
PVDD
3
NC
4, 9, 10, 11, 12
SW
2, 5, 6, 7, 8, 21
PGND
13,14,15,
16,17,18,19
20
PVIN
BST
22
CS
Pin Function
5V Internal Linear Regulator (Output): PVDD supply is the power MOSFET gate drive supply voltage
and created by internal LDO from V_IN. When V_IN < +5.5V, PVDD should be tied to PVIN pins.
A 2.2µF ceramic capacitor from the PVDD pin-to-PGND (pin 2) must be place next to the IC.
No Connect.
Switch Node (Output): Internal connection for the high-side MOSFET source and low-side MOSFET
drain. Due to the high speed switching on this pin, the SW pin should be routed away from sensitive
nodes.
Power Ground. PGND is the ground path for the MIC26903 buck converter power stage. The
PGND pins connect to the low-side N-Channel internal MOSFET gate drive supply ground, the
sources of the MOSFETs, the negative terminals of input capacitors, and the negative terminals of
output capacitors. The loop for the power ground should be as small as possible and separate from
the Signal ground (SGND) loop.
High-Side N-internal MOSFET Drain Connection (Input): The PV_IN operating voltage range is from
4.5V to 26V. Input capacitors between the PVIN pins and the power ground (PGND) are required
and keep the connection short.
Boost (Output): Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode
is connected between the PVDD pin and the BST pin. A boost capacitor of 0.1μF is connected
between the BST pin and the SW pin. Adding a small resistor at the BST pin can slow down the
turn-on time of high-side N-Channel MOSFETs.
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.
July 2011
2
M9999-071311-A