MIC26903-ZA 28V, 9A Hyper Speed Control Synchronous DC-to-DC Buck Regulator SuperSwitcher II General Description The Micrel MIC26903-ZA is a constant-frequency, synchronous buck regulator featuring a unique adaptive on-time control architecture. The MIC26903-ZA operates SuperSwitcher II over an input supply range of 4.5V to 28V and provides a regulated output of up to 9A of output current. The output Features voltage is adjustable down to 0.6V with a guaranteed accuracy of 1%, and the device operates at a switching Hyper Speed Control architecture enables frequency of 600kHz. High Delta V operation (V = 28V and V = 0.6V) IN OUT Micrels Hyper Speed Control architecture allows for Small output capacitance ultra-fast transient response while reducing the output 4.5V to 28V voltage input capacitance and also makes (High V )/(Low V ) IN OUT 9A output current capability and 95% peak efficiency operation possible. This adaptive t ripple control ON Adjustable output from 0.6V to 5.5V architecture combines the advantages of fixed-frequency 1% feedback accuracy operation and fast transient response in a single device. Any Capacitor stable - zero-to-high ESR The MIC26903-ZA offers a full suite of features to ensure 600kHz switching frequency protection of the IC during fault conditions. These include undervoltage lockout to ensure proper operation under No external compensation power-sag conditions, internal soft-start to reduce inrush Power Good (PG) output current, foldback current limit, hiccup mode short-circuit Foldback I-limit and hiccup short-circuit protection protection, and thermal shutdown. An open-drain Power Supports safe startup into a pre-biased load Good (PG) pin is provided. 40C to +125C junction temperature range Datasheets and support documentation are available on 28-pin 5mm 6mm QFN package Micrels web site at: www.micrel.com. Applications Distributed POL and telecom/networking infrastructure Printers, scanners, graphic and video cards Set-top boxes, gateways and routers Typical Application Efficiency (V = 12V) IN vs. Output Current 100 95 5.0V 90 3.3V 2.5V 85 1.8V 80 1.5V 1.2V 75 1.0V 70 0.9V 65 60 V = 12V IN 55 50 0246 8 10 12 OUTPUT CURRENT (A) Hyper Speed Control, SuperSwitcher II, and Any Capacitor are trademarks of Micrel, Inc. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC26903-ZA Ordering Information Switching Junction Temperature Lead Part Number Voltage Package Frequency Range Finish MIC26903-ZAYJL Adjustable 600kHz 28-Pin 5mm 6mm QFN 40C to +125C Pb-Free Pin Configuration 28-Pin 5mm 6mm QFN (JL) (Top View) 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 created by internal LDO from VIN. When VIN < +5.5V, PVDD should be tied to the PVIN pins. A 2.2F ceramic capacitor from the PVDD pin to PGND (pin 2) must be placed next to the IC. Power Ground: PGND is the ground path for the 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, 2, 5, 6, PGND the negative terminals of input capacitors, and the negative terminals of output capacitors. The loop 7, 8, 21 for the power ground should be as small as possible and separate from the signal ground (SGND) loop. 3 NC No Connect. Switch Node output: Internal connection for the high-side MOSFET source and low-side MOSFET 4, 9, SW drain. Because of the high-speed switching on this pin, the SW pin should be routed away from 10, 11, 12 sensitive nodes. High-Side N-Internal MOSFET Drain Connection input: The PVIN operating voltage range is from 4.5V 13,14,15, PVIN to 28V. Input capacitors between the PVIN pins and the power ground (PGND) are required and keep 16,17,18,19 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 between 20 BST the BST pin and the SW pin. Adding a small resistor at the BST pin can reduce the turn-on time of high-side N-Channel MOSFETs. Revision 1.1 July 22, 2014 2