MIC2124YMM Microchip

MIC2124 Constant Frequency, Synchronous Current Mode Buck Controller Hyper Speed Control Family General Description Features The Micrel MIC2124 is a member of the Hyper Speed +3V to +18V input voltage Control family of DC-DC controllers. It uses an adaptive 25A output current capability TM on-time current mode control scheme and operates at a Any Capacitor stable constant frequency. - Zero ESR to high ESR The MIC2124 operates over a supply range of +3V to Output down to 0.8V with 1% FB accuracy +18V, and is independent of the IC supply voltage V . It IN Up to 94% efficiency operates at a fixed 300kHz switching frequency and can 300kHz switching frequency be used to provide up to 25A of output current. The output All N-Channel MOSFET design voltage is adjustable down to +0.8V. Shutdown feature with EN/COMP The MIC2124 includes an EN/COMP pin that can be No current-sense resistor needed pulled low to shut down the converter. The MIC2124 Internal 4ms digital soft-start optimizes performance and ensures stability with external Thermal shutdown compensation. Pre-bias output safe The UVLO is provided to ensure proper operation under Cycle-by-Cycle foldback current-limit protection power-sag conditions and to make sure that the external 10-pin MSOP package power MOSFET has enough voltage to work with. An internal digital soft-start ensures reduced inrush current. 40C to +125C junction temperature range Cycle-by-cycle current limiting ensures FET protection. The MIC2124 is available in a 10-pin MSOP package with Applications a junction temperature operating range from 40C to Printers and scanners +125C. Graphic and video cards PCs and servers Microprocessor core supply Low-voltage distributed power Telecommunication and networking Set-top box, gateways and router Typical Application 12V to 3.3V Efficiency 100 90 80 70 V = 12V HSD V = 5V IN 60 02 46 8 10 OUTPUT CURRENT (A) MIC2124 Adjustable Output 300kHz Buck Converter 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. MIC2124 Ordering Information Part Number Voltage Switching Frequency Junction Temp. Range Package Lead Finish MIC2124YMM Adj. 300kHz 40 to +125C 10-Pin MSOP Pb-Free Pin Configuration 10-Pin MSOP (MM) Pin Description Pin Number Pin Name Pin Function 1 HSD High-Side N-MOSFET Drain Connection (Input): Input voltage for the internal sensing of external power stage supply. The HSD operating voltage range is from 3V to 18V. Input capacitors between HSD and the power ground (PGND) are required. 2 EN/COMP Enable (Input): Floating = enable, logic low = shutdown. In the off state, supply current of the device is greatly reduced (typically 1mA). COMP (Output): Output of the gm error amplifier and connects to the components for the external compensation. 3 FB Feedback (Input): Input to the transconductance amplifier of the control loop. The FB pin is regulated to 0.8V. A resistor divider connecting the feedback to the output is used to adjust the desired output voltage. 4 GND Signal ground. GND is the ground path for the device input voltage V and the control circuitry. The IN loop for the signal ground should be separate from the power ground (PGND) loop. 5 IN Input Voltage (Input): Power to the internal reference and control sections of the MIC2124. The IN operating voltage range is from 3V to 5.5V. A 2.2F ceramic capacitors from IN to GND are recommended for clean operation. Connect IN to HSD when V < 5.5V. HSD 6 DL Low-Side Drive (Output): High-current driver output for external low-side MOSFET. The DL driving voltage swings from ground-to-IN. 7 PGND Power Ground. PGND is the ground path for the MIC2124 buck converter power stage. The PGND pin connects to the sources of low-side N-Channel 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 (GND) loop. 8 DH 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 V to V . LX BST 9 LX Switch Node (Input): High-current output driver return. The LX pin connects directly to the switch node. Due to the high speed switching on this pin, the LX pin should be routed away from sensitive nodes. Current Sense input (Input): LX pin also senses the current for the current mode control and short circuit protection by monitoring the voltage across the low-side MOSFET during OFF time. In order to sense the current accurately, connect the low-side MOSFET drain to LX using a Kelvin connection. 10 BST Boost (Output): Bootstrapped voltage to the high-side N-channel MOSFET driver. A Schottky diode is connected between the IN pin and the BST pin. A boost capacitor of 0.1 F is connected between the BST pin and the LX pin. Adding a small resistor at BST pin can slow down the turn-on time of high- side N-Channel MOSFETs. 2 M9999-060810-D June 2010