MIC26950 TM 12A Hyper Speed Control Synchronous DC-DC Buck Regulator TM SuperSwitcher II General Description Features TM Hyper Speed Control architecture enables The Micrel MIC26950 is a constant-frequency, synchronous buck regulator featuring a unique digitally modified adaptive - High delta V operation (V = 26V and V = 0.8V) IN OUT ON-time control architecture. The MIC26950 operates over - Small output capacitance an input supply range of 4.5V to 26V and provides a 4.5V to 26V input voltage regulated output at up to 12A of output current. The output Adjustable output from 0.8V to 5.5V ( 1% accuracy) voltage is adjustable down to 0.8V with a typical accuracy of TM Any Capacitor Stable 1%, and the device operates at a switching frequency of - Zero-ESR to high-ESR output capacitance 300kHz. TM 12A output current capability Micrels Hyper Speed Control architecture allows for ultra- 300kHz switching frequency fast transient response while reducing the output capacitance and also makes (High V )/(Low V ) operation possible. IN OUT Internal compensation ripple control architecture This digitally modified adaptive t ON Up to 95% efficiency combines the advantages of fixed-frequency operation and 6ms internal soft-start fast transient response in a single device. Foldback current-limit and hiccup mode short-circuit The MIC26950 offers a full suite of protection features to protection ensure protection of the IC during fault conditions. These Thermal shutdown include undervoltage lockout to ensure proper operation Supports safe start-up into a pre-biased load under power-sag conditions, internal soft-start to reduce inrush current, fold-back current limit, hiccup mode short- 40 C to +125 C junction temperature range circuit protection and thermal shutdown. 28-pin 5mm X 6mm MLF package All support documentation can be found on Micrels web site at: www.micrel.com. Applications Distributed power systems Communications/networking infrastructure Set-top box, gateways and routers Printers, scanners, graphic cards and video cards Typical Application Efficiency (V = 12V) IN vs. Output Current 100 95 5.0V 3.3V 90 2.5V 85 1.5V 80 1.0V 75 70 65 60 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. MIC26950 Ordering Information Junction Temperature Part Number Voltage Switching Frequency Package Lead Finish Range MIC26950YJL Adjustable 300kHz 40C to +125C 28-pin 5mm 6mm MLF Pb-Free Pin Configuration 28-Pin 5mm X 6mm MLF (YJL) Pin Description Pin Pin Name Pin Function Number 13,14,15, High-Side N-internal MOSFET Drain Connection (Input): The PV operating voltage range is from IN 16,17,18, PVIN 4.5V to 26V. Input capacitors between PV and the power ground (PGND) are required. IN 19 Enable (Input): A logic level control of the output. The EN pin is CMOS-compatible. Logic high or 24 EN floating = enable, logic low = shutdown. In the off state, supply current of the device is greatly reduced (typically 0.8mA). Feedback (Input): Input to the transconductance amplifier of the control loop. The FB pin is regulated 25 FB to 0.8V. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. Signal ground. SGND must be connected directly to the ground planes. Do not route the SGND pin to 26 SGND the PGND Pad on the top layer. V Bias (Input): Power to the internal reference and control sections of the MIC26950. The V DD DD 27 VDD operating voltage range is from 4.5V to 5.5V. A 2.2F ceramic capacitor from the VDD pin-to-PGND is recommended for clean operation. Power Ground. PGND is the ground path for the MIC26950 buck converter power stage. The PGND 2, 5, 6, pin connects to the sources of low-side N-Channel internal MOSFETs, the negative terminals of input PGND 7, 8, 21 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. Current Sense (Input): High current output driver return. The CS pin connects directly to the switch node. Due to the high speed switching on this pin, the CS pin should be routed away from sensitive 22 CS nodes. CS pin also senses the current by monitoring the voltage across the low-side internal MOSFET during OFF-time. 2 July 2011 M9999-070111-C