MIC2174/MIC2174C Synchronous Buck Controller Featuring Adaptive On-Time Control 40V Input, 300kHz Hyper Speed Control Family General Description Features The Micrel MIC2174/MIC2174C is a fixed-frequency, Hyper Speed Control architecture enables: synchronous buck controller featuring adaptive on-time High delta V operation (V = 40V and V = 0.8V) HSD OUT control. The MIC2174/MIC2174C operates over an input Smaller output capacitors than competitors supply range of 3V to 40V at a fixed switching frequency of 3V to 40V input voltage 300kHz and is capable of driving 25A of output current. TM Any Capacitor stable The output voltage is adjustable down to 0.8V. - Zero ESR to high ESR A unique Hyper Speed Control architecture allows for 300kHz switching frequency ultra-fast transient response while reducing the output capacitance. It also makes ultra-fast transient response Adjustable output from 0.8V to 5.5V (V 28V) HSD while reducing the output capacitance and also allows for Adjustable output from 0.8V to 3.6V (V > 28V) HSD extremely low duty-cycle operation. The MIC2174 / 1% FB accuracy (MIC2174) MIC2174C utilizes an adaptive T ripple controlled ON 3% FB accuracy (MIC2174C) architecture. A UVLO is provided to ensure proper operation under power-sag conditions to prevent the Up to 94% efficiency external power MOSFET from overheating. A soft-start is Foldback current limit and hiccup mode short-circuit provided to reduce inrush current. Foldback current limit protection and hiccup mode short-circuit protection ensure FET and Thermal shutdown load protection. Safe start-up into pre-biased loads The MIC2174/MIC2174C is available in a 10-pin MSOP 40 C to +125 C junction temperature range (MAX1954A-compatible) package with an operating junction temperature range from 40 C to +125 C. Applications All support documentation can be found on Micrels web Telecom Networking site at: www.micrel.com. Industrial Equipment Distributed DC power systems Typical Application 12V to 3.3V Efficiency 100 95 90 85 80 75 70 65 60 VIN=5V 55 50 02 46 8 10 OUTPUT CURRENT (A) Synchronous Buck Controller Featuring Adaptive On-Time Control Hyper Speed Control 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. MIC2174/MIC2174C Ordering Information Junction Temperature Part Number Voltage Accuracy Switching Frequency Package Lead Finish Range MIC2174-1YMM Adj. 1% 300kHz 40 to +125C 10-Pin MSOP Pb-Free MIC2174C-1YMM Adj. 3% 270kHz 40 to +125C 10-Pin MSOP Pb-Free Pin Configuration 10-Pin MSOP (MM) Pin Description Pin Number Pin Name Pin Function High-Side N-MOSFET Drain Connection (input): Power to the drain of the external high-side N- 1 HSD channel MOSFET. The HSD operating voltage range is from 3V to 40V. Input capacitors between HSD and the power ground (PGND) are required. Enable (input): A logic level control of the output. The EN pin is CMOS-compatible. Logic high or 2 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 3 FB to 0.8V. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. Signal ground. GND is the ground path for the device input voltage V and the control circuitry. The IN 4 GND loop for the signal ground should be separate from the power ground (PGND) loop. Input Voltage (input): Power to the internal reference and control sections of the MIC2174/MIC2174C. The IN operating voltage range is from 3V to 5.5V. A 2.2F ceramic capacitors from IN to GND are 5 IN recommended for clean operation. V must be powered up no earlier than V to make the soft-start IN HSD function behavior correctly. Low-Side Drive (output): High-current driver output for external low-side MOSFET. The DL driving 6 DL voltage swings from ground to IN. Power Ground. PGND is the ground path for the MIC2174/MIC2174C buck converter power stage. The PGND pin connects to the sources of low-side N-Channel MOSFETs, the negative terminals of 7 PGND 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 (GND) loop. High-Side Drive (output): High-current driver output for external high-side MOSFET. The DH driving voltage is floating on the switch node voltage (LX). It swings from ground to V minus the diode drop. IN 8 DH Adding a small resistor between DH pin and the gate of the high-side N-channel MOSFETs can slow down the turn-on and turn-off time of the MOSFETs. 2 September 2010 M9999-091310-C