MIC261201 28V, 12A Hyper Speed Control Synchronous DC/DC Buck Regulator SuperSwitcher II General Description Features Hyper Speed Control architecture enables The Micrel MIC261201 is a constant-frequency, synchronous buck regulator featuring a unique adaptive on-time control - High Delta V operation (V = 28V and V = 0.8V) IN OUT architecture. The MIC261201 operates over an input supply - Small output capacitance range of 4.5V to 28V and provides a regulated output of up to 4.5V to 28V voltage input 12A of output current. The output voltage is adjustable down 12A output current capability, up to 95% efficiency to 0.8V with a guaranteed accuracy of 1%, and the device Adjustable output from 0.8V to 5.5V operates at a switching frequency of 600kHz. 1% feedback accuracy Micrels Hyper Speed Control architecture allows for ultra- Any Capacitor Stable zero-to-high ESR fast transient response while reducing the output capacitance and also makes (High V )/(Low V ) operation possible. 600kHz switching frequency IN OUT This adaptive t ripple control architecture combines the ON No external compensation advantages of fixed-frequency operation and fast transient Power Good (PG) output response in a single device. Foldback current-limit and hiccup mode short-circuit The MIC261201 offers a full suite of protection features to protection ensure protection of the IC during fault conditions. These Supports safe startup into a pre-biased load include undervoltage lockout to ensure proper operation 40 C to +125 C junction temperature range under power-sag conditions, internal soft-start to reduce 28-pin 5mm 6mm MLF package inrush current, foldback current limit, hiccup mode short- circuit protection and thermal shutdown. An open-drain Power Good (PG) pin is provided. Applications All support documentation can be found on Micrels web Distributed power systems site at: www.micrel.com. Communications/networking infrastructure Set-top box, gateways and routers Printers, scanners, graphic cards and video card Typical Application Efficiency (V = 12V) IN vs. Output Current 100 95 5.0V 3.3V 90 2.5V 1.8V 85 1.5V 80 1.2V 1.0V 75 0.9V 70 0.8V 65 60 VIN = 12V 55 50 03 69 12 15 OUTPUT CURRENT (A) Hyper Speed Control, SuperSwitcher II, and Any Capacitor are trademarks of Micrel, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC261201 Ordering Information Junction Temperature Part Number Voltage Switching Frequency Package Lead Finish Range MIC261201YJL Adjustable 600kHz 40C to +125C 28-Pin 5mm 6mm MLF Pb-Free Pin Configuration 28-Pin 5mm 6mm MLF (YJL) Pin Description Pin Number Pin Name Pin Function 5V Internal Linear Regulator (Output): PVDD supply is the power MOSFET gate drive supply voltage and created by internal LDO from V . When V < +5.5V, PVDD should be tied to PVIN pins. A 2.2F 1 PVDD IN IN ceramic capacitor from the PVDD pin to PGND (pin 2) must be place next to the IC. 3 NC No Connect. Switch Node (Output): Internal connection for the high-side MOSFET source and low-side MOSFET 4, 9, 10, 11, SW drain. Due to the high speed switching on this pin, the SW pin should be routed away from sensitive 12 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 2, 5, 6, 7, 8, PGND sources of the MOSFETs, the negative terminals of input capacitors, and the negative terminals of 21 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 operating voltage range is from IN 13,14,15, PVIN 4.5V to 28V. Input capacitors between the PVIN pins and the power ground (PGND) are required 16,17,18,19 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 0.1F is connected 20 BST 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. In order 22 CS 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 MOSFETs output driver return. 2 July 2011 M9999-071311-A