Micrel, Inc. MIC2179 MIC2179 1.5A Synchronous Buck Regulator General Description Features The Micrel MIC2179 is a 200kHz synchronous buck (step- 4.5V to 16.5V input voltage range down) switching regulator designed for high-efficiency, bat- Dual-mode operation for high efficiency (up to 96%) tery-powered applications. PWM mode for > 150mA load current Skip mode for <150mA load current The MIC2179 operates from a 4.5V to 16.5V input and features 150m internal power MOSFETs at 12V input internal power MOSFETs that can supply up to 1.5A output 200kHz preset switching frequency current. It can operate with a maximum duty cycle of 100% Low quiescent current for use in low-dropout conditions. It also features a shutdown 1.0mA in PWM mode mode that reduces quiescent current to less than 5A. 600A in skip mode The MIC2179 achieves high efficiency over a wide output < 5A in shutdown mode current range by operating in either PWM or skip mode. The Current-mode control operating mode is externally selected, typically by an intel- Simplified loop compensation ligent system, which chooses the appropriate mode according Superior line regulation to operating conditions, efficiency, and noise requirements. 100% duty cycle for low dropout operation The switching frequency is preset to 200kHz and can be Current limit synchronized to an external clock signal of up to 300kHz. Thermal shutdown The MIC2179 uses current-mode control with internal current Undervoltage lockout sensing. Current-mode control provides superior line regula- Applications tion and makes the regulator control loop easy to compensate. The output is protected with pulse-by-pulse current limiting High-efficiency, battery-powered supplies and thermal shutdown. Undervoltage lockout turns the output Buck (step-down) dc-to-dc converters off when the input voltage is less than 4.5V. Cellular telephones Laptop computers The MIC2179 and is packaged in a 20-lead SSOP package Hand-held instruments with an operating temperature range of 40C to +85C. Battery Charger Typical Application V IN 5.4V to 16.5V C1 10F U1 16,17 20V R1 L1 VIN 20k 15 22H EN 3,4 V OUT SW 3.3V/600mA 6 Output Good D1 PWRGD 1,2, C2 Output Low MBRM120 MIC 19,20 100F PGND Skip Mode 5 2179-3.3 6.3V PWM PWM Mode 13 7 SYNC FB COMP SGND BIAS 8 912 14 C3 R5 Pins 4 and 18 are not connected. 0.01F C4 4.02k 6.8nF Pins 3 and 4 can be connected together for a low-impedance connection. Micrel, Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC2179 Ordering Information Part Number Voltage Temperature Range Package Standard* Pb-Free MIC2179BSM MIC2179YSM Adj. -40C to +85C 20-Lead SSOP MIC2179-3.3BSM MIC2179-3.3YSM 3.3V -40C to +85C 20-Lead SSOP MIC2179-5.0BSM MIC2179-5.0YSM 5.0V -40C to +85C 20-Lead SSOP * Standard product will be supported as Pb-Free IAW PCCN 040004 effective 1-1-2005 pending residual depletion. Pin Configuration PGND 1 20 PGND PGND PGND 2 19 SW 3 18 NC NC 4 17 VIN VIN 5 16 PWM PWRGD 6 15 EN FB 7 14 BIAS COMP SYNC 8 13 SGND SGND 9 12 SGND 10 11 SGND 20-Lead Wide SSOP Pin Description Pin Number Pin Name Pin Function 1, 2, 19, 20 PGND Power Ground: Connect all pins to central ground point. 3 SW Switch (Output): Internal power MOSFET output switches. 5 PWM PWM/Skip-Mode Control (Input): Logic-level input. Controls regulator operating mode. Logic low enables PWM mode. Logic high enables skip mode. Do not allow pin to float. 6 PWRGD Error Flag (Output): Open-drain output. Active low when FB input is 10% below the reference voltage (V ). REF 7 FB Feedback (Input): Connect to output voltage divider resistors. 8 COMP Compensation: Output of internal error amplifier. Connect capacitor or series RC network to compensate the regulator control loop. 912 SGND Signal Ground: Connect all pins to ground, PGND. 13 SYNC Frequency Synchronization (Input): Optional. Connect an external clock signal to synchronize the oscillator. Leading edge of signal above 1.7V terminates switching cycle. Connect to SGND if not used. 14 BIAS Internal 3.3V Bias Supply: Decouple with 0.01F bypass capacitor to SGND. Do not apply any external load. 15 EN Enable (Input): Logic high enables operation. Logic low shuts down regulator. Do not allow pin to float. 16, 17 VIN Supply Voltage (Input): Requires bypass capacitor to PGND. Both pins must be connected to V . IN 4, 18 NC not internally connected. June 2009 2 M9999-063009