MIC261203 28V, 12A Hyper Light Load Synchronous DC/DC Buck Regulator SuperSwitcher IIG General Description Features Hyper Light Load efficiency up to 80% at 10mA The Micrel MIC261203 is a constant-frequency, synchronous DC/DC buck regulator featuring adaptive on- Hyper Speed Control architecture enables time control architecture. The MIC261203 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. MIC261203 operates at a constant 600kHz switching frequency in continuous- Output current up to 12A conduction mode and can be used to provide up to 12A of Up to 95% efficiency output current. The output voltage is adjustable down to Adjustable output voltage from 0.8V to 5.5V 0.8V. 1% FB accuracy Micrels Hyper Light Load architecture provides the same TM Any Capacitor stable zero-to-high ESR high-efficiency and ultra-fast transient response as the 600kHz switching frequency Hyper Speed Control architecture under medium to heavy loads, but also maintains high efficiency under light load Power Good (PG) output conditions by transitioning to variable frequency, Foldback current-limit and hiccup mode short-circuit discontinuous mode operation. protection The MIC261203 offers a full suite of protection features to Safe start-up into pre-biased loads ensure protection of the IC during fault conditions. These 5mm x 6mm MLF package include undervoltage lockout to ensure proper operation 40 C to +125 C junction temperature range under power-sag conditions, thermal shutdown, internal soft start to reduce the inrush current, foldback current- Applications limit and hiccup mode short-circuit protection. The MIC261203 includes a Power Good (PG) output to allow Distributed power systems simple sequencing. Telecom/networking infrastructure All support documentation can be found on Micrels web Printers, scanners, graphic cards and video cards site at: www.micrel.com. Typical Application Efficiency (V = 12V) IN vs. Output Current 100 95 5.0V 90 3.3V 2.5V 85 1.8V 1.5V 80 1.2V 75 1.0V 0.9V 70 0.8V 65 60 55 V = 12V IN 50 0 369 12 15 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. MIC261203 Ordering Information Junction Temperature Part Number Voltage Switching Frequency Package Lead Finish Range MIC261203YJL Adjustable 600kHz 40C to +125 C 28-Pin 5mm x 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 1 PVDD and created by internal LDO from V . When V < +5.5V, PVDD should be tied to PVIN pins. IN IN 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 MOSFET 4, 9, 10, 11, 12 SW 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. 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 22 CS 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 MOSFETs output driver return. 2 July 2011 M9999-071311-A