MIC26903 28V, 9A Hyper Light Load Synchronous DC/DC Buck Regulator SuperSwitcher IIG General Description Features Hyper Light Load efficiency up to 80% at 10mA The Micrel MIC26903 is a constant-frequency, synchronous DC/DC buck regulator featuring adaptive on- Hyper Speed Control architecture enables time control architecture. The MIC26903 operates over a High delta V operation (V = 28V and V = 0.8V) IN OUT supply range of 4.5V to 28V. It has an internal linear Small output capacitance regulator which provides a regulated 5V to power the Input voltage range: 4.5V to 28V internal control circuitry. MIC26903 operates at a constant 600kHz switching frequency in continuous conduction Output current up to 9A mode and can be used to provide up to 9A of output Up to 95% efficiency current. The output voltage is adjustable down to 0.8V. Adjustable output voltage from 0.8V to 5.5V Micrels Hyper Light Load architecture provides the same 1% FB accuracy high-efficiency and ultra-fast transient response as the TM Any Capacitor stable zero-to-high ESR Hyper Speed Control architecture under medium to heavy 600kHz switching frequency loads, but also maintains high efficiency under light load conditions by transitioning to variable frequency, Power Good (PG) output discontinuous mode operation. Foldback current-limit and hiccup mode short-circuit The MIC26903 offers a full suite of protection features to protection ensure protection of the IC during fault conditions. These Safe start-up into pre-biased loads include undervoltage lockout to ensure proper operation 5mm 6mm MLF package under power-sag conditions, thermal shutdown, internal 40 C to +125 C junction temperature range soft-start to reduce the inrush current, foldback current limit and hiccup mode short-circuit protection. The Applications MIC26903 includes a Power Good (PG) output to allow simple sequencing. Distributed power systems All support documentation can be found on Micrels web Telecom/networking infrastructure site at: www.micrel.com. Printers, scanners, graphic cards and video cards Typical Application Efficiency (V = 12V) IN vs. Output Current 100 5.0V 95 3.3V 90 2.5V 1.8V 85 1.5V 80 1.2V 1.0V 75 0.9V 0.8V 70 65 V = 12V IN 60 55 50 03 69 12 OUTPUT CURRENT (A) Hyper Speed Control, Hyper Light Load, 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. MIC26903 Ordering Information Junction Temperature Part Number Voltage Switching Frequency Package Lead Finish Range MIC26903YJL Adjustable 600kHz 40C to +125 C 28-Pin 5mm 6mm MLF Pb-Free Pin Configuration 28-Pin 5mm x 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 IN IN 1 PVDD pins. A 2.2F 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 4, 9, 10, 11, 12 SW 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 2, 5, 6, 7, 8, 21 PGND 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 operating voltage range is from IN 13,14,15, PVIN 4.5V to 26V. 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. 2 July 2011 M9999-071311-A