Si9177 New Product Vishay Siliconix 200-mA PSM Step Down Converter with Bypass Capability FEATURES APPLICATIONS 2.7-V to 6-V Input Voltage Range 1.2-V to 5-V Output Efficiency of 95% for VOUT of 3.3 V @ 200-mA Load Selectable Pulse Skipping Modulation (PSM) or Bypass Mode (BP) Operation 150-mW Bypass Switch for 800-mA Loads Integrated MOSFET with Low External Part Count Shutdown Current <1 mA Integrated UVLO and Power on Reset Integrated Soft-Start Over Temperature Protection MLP33-10 or MSOP-10 Packages Cellular Phones, Cordless Phones Computer Point of Use, Notebook PDAs Battery Powered Devices MP3 Players DESCRIPTION The Si9177 is a dual-mode power adjustable output converter. When it is set to PSM mode, the Si9177 operates as a pulse-skipping-modulation controlled step-down (buck) converter with an output voltage range of 1.2 V to 5 V. It has an integrated MOSFET, capable of supplying 200-mA load current with a 1.5-mH inductor. The output voltage is adjusted by a resistive divider on the FB pin. The typical conversion efficiency is above 90%. A logic HIGH at the BP/PSM pin puts Si9177 in bypass mode. The main PMOS buck switch is forced to turn on at 100% duty cycle, overriding the FB signal. The voltage differential between input and output is the resistive voltage drop on the internal 150-mW PMOS and the inductor. The Si9177 delivers 800-mA load in bypass mode. The Si9177 is available in the space saving MLP33-10 and MSOP-10 packages. In order to satisfy the stringent ambient temperature requirements, the Si9177 is rated to handle the industrial temperature range of -25C to 85C. TYPICAL APPLICATION CIRCUIT 1 VIN 2 CIN 10 VIN LX VIN LX SI9177 ON/OFF BP/PSM 3 4 5 Document Number: 70312 S-03663—Rev. B, 07-Apr-03 GND ENABLE FB BP/PSM REF NC 9 8 1.5 mH VOUT COUT R1 7 6 CREF R2 www.vishay.com 1 Si9177 New Product Vishay Siliconix ABSOLUTE MAXIMUM RATINGS (TA = 25C) VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 V BP/PSM, ENABLE, FB, LX . . . . . . . . . . . . . . . . . . . . . . . . - 0.3 V to VIN + 0.3 V Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 55 to 150C Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150C Power Dissipation (Package)a. MLP33-10b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 mW MSOP-10c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915 mW Thermal Impedance (QJA) MLP33-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135C/W MSOP-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71C/W Notes a. Device mounted with all leads soldered or welded to PC board. b. Derate 7.4 mW/ C above 25C. c. Derate 14 mW/ C above 25C. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED OPERATING RANGE VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 V to 6 V Inductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 mH CIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mF CREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Open COUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 mF Operating Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . - 25 to 85 C SPECIFICATIONS Test Conditions Unless Specified Parameter Symbol - 40C to 85C 85C, VIN = VDD, DD , CIN = 10 mF COUT = 4.7 mF, L = 2.2 mH, 2.6 V v VIN v 5.5 V R1 = 11.3 kW, R2 = 20 kW Limits Mina Typb Maxa Unit 6 V Converter Operation Input Voltage VIN 2.7 Maximum Bypass Mode Current Maximum PSM Mode Current 800 IOUT MOSFET On-resistance rDS(on) Power Supply Rejection PSRR Feedback Voltage VFB mA 200 VIN w 3.3 V 150 300 60 mW dB IREF = 0 1.175 1.215 1.255 IREF = 0, TA = 25C 1.195 1.215 1.235 V Start-Up Start-Up Delay Time Soft Start Time tDELAY CREF = 0.1 mF, See Figure 1 5 ms tss See Figure 1 100 ms ENABLE, BP/PSM Logic High VIH Logic Low VIL Input Current 1.5 0.4 IIH ENABLE, BP/PSM = VIN 1 IIL ENABLE, BP/PSM = GND 1 V mA Protection Under Voltage Lockout VUVLO Under Voltage Lockout Hysteresis VHUVLO Thermal Shutdown Thermal Shutdown Hysteresis 2.2 2.35 2.5 V 0.1 TSD Temperature rising 165 THSD VIN = 3.3 V 25 C Supply Current BP Mode PSM Mode Shutdown IIN VIN = 3.3 33V 75 110 190 250 VIN = 3.3 V, ENABLE = 0 V mA 1 Notes a. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum, is used in this data sheet. b. Typical values are for DESIGN AID ONLY, not guaranteed or subject to production testing. c. Guaranteed by design and characterization, not subject to production testing. www.vishay.com 2 Document Number: 70312 S-03663—Rev. B, 07-Apr-03 Si9177 New Product Vishay Siliconix PIN CONFIGURATION MSOP-10 VIN 1 10 LX VIN 2 9 LX ENABLE 3 8 GND BP/PSM 4 7 FB Si9177BM TI Si9177BM-TI NC 5 6 REF Si9177BH-TI ORDERING INFORMATION Part Number Top View Temperature Range Package - 25C to 85C Tape and Reel Eval Kit Temperature Range Board Type Si9177DB - 25C to 85C Surface Mount MLP33 VIN VIN 10 9 8 7 6 2 3 4 5 ENABLE BP/PSM NC LX LX GND FB REF Top View PIN DESCRIPTION Pin No. Name 1, 2 VIN Function 3 ENABLE Logic high enables the converter. Logic low shuts down the IC and decreases current consumed to <1 mA. 4 BP/PSM Logic high = Bypass mode, logic low = PSM mode. 5 NC No Connection 6 REF 1.215-V reference. 7 FB 8 GND 9, 10 LX Input voltage source for buck converter, MOSFET driver, and IC control circuits. Direct output voltage sense feedback IC ground Inductor connection node TIMING WAVEFORMS 90% VOUT 10% tDELAY = Start-Up Delay Time tSS = Soft-Start Time VIN t DELAY t SS FIGURE 1. Soft-Start Timing Document Number: 70312 S-03663—Rev. B, 07-Apr-03 www.vishay.com 3 Si9177 New Product Vishay Siliconix FUNCTIONAL BLOCK DIAGRAM VIN VIN Reference Generator REF UVLO POR BP/PSM BP ENABLE LX PSM/BP Controller Driver PSM LX VADJ Turn-On Control NC + FB - Zero Current Detect + - + Turn off Control Peak Current Comparater 0.6 A GND APPLICATION CIRCUIT 1 VIN CIN 10 mF 2 10 VIN LX VIN LX SI9177 ON/OFF BP/PSM 3 4 5 GND ENABLE FB BP/PSM REF 9 8 1.5 mH VOUT COUT 10 mF R1 7 6 R2 CREF NC MLP33-10 www.vishay.com 4 Document Number: 70312 S-03663—Rev. B, 07-Apr-03 Si9177 New Product Vishay Siliconix DETAIL OPERATIONAL DESCRIPTION Start-Up When voltage is first applied to the VIN pin, the UVLO circuitry prevents the internal p-channel MOSFET from turning on. Once the VIN voltage exceeds the UVLO threshold of 2.4 V, and with no other shutdown condition detected, an internal power-on-reset timer is activated to delay the start of switching if the BP/PSM pin is held a logic LOW level. The amount of delay is set by the capacitor CREF on the REF pin and the peak current in the inductor is limited to 600 mA. If the BP/PSM pin has a logic HIGH applied, then Bypass Mode soft-start is achieved by gradually turning on the p-channel MOSFET in 40 µs insuring that the output voltage rises smoothly. Pulse Skipping Mode Si9177 is designed to operate with light loads. When the BP/PSM pin is connected to logic LOW level, the Si9177 operates in pulse-skipping mode. PSM enhances efficiency in light load conditions when compared to fixed frequency PWM mode because switch conduction losses, gate charge and switching losses are reduced. By delivering energy to the load only when needed, the p-channel MOSFET gate capacitance is charged and discharged less frequently and MOSFET conduction loss is minimized thereby reducing total losses and increasing converter efficiency. In PSM, the switching frequency, fSW, increases as and decreases as the load current increases and decreases. The typical conversion efficiency in PSM mode is 90%. load. This mode is enabled by setting the BP/PSM pin to a logic HIGH. In this mode the IC ignores the feedback signal at the FB pin, forcing the internal p-channel MOSFET to turn on continuously. The input-to-output voltage differential is reduced to the voltage drop across the 150-mΩ MOSFET and the inductor. Si9177 can bypass 800 mA at 95% typical efficiency or provide nearly the entire input voltage to the load. Whenever the converter enters BYPASS mode, the p-channel MOSFET turns on gradually within 40 µs to reduce surge current to the input capacitor. Shutdown Si9177 is designed to conserve as much battery life as possible by decreasing current consumption during normal operation, as well as the shutdown mode. With logic LOW level on the ENABLE pin, the current consumption of the IC is decreases to less than 1 µA by shutting off all circuits. A logic HIGH enables the controller, allowing start up as described in the “Start-Up” section above. Reference and Power-On-Reset Timer The reference voltage of Si9177 is set to 1.215 V. It is internally connected to the non-inverting input of the error amplifier. The power on reset delay time is set by the capacitance on the REF pin and can be determined from the following relationship: tPORDELAY = 4 By operating as a constant on-time converter, the Si9177 achieves PSM operation. The p-channel MOSFET switching transistor is turned on to deliver energy to the load. The switch remains on for the minimum on-time or until the inductor current reaches 600 mA. If the applied on-time is sufficient to increase the output voltage above the in-regulation set point (FB pin voltage is greater than VFB), the p-channel MOSFET turns off for a minimum off-time and continues to apply constant on-time pulses to insure regulation is maintained. If the on-time of the p-channel switch causes the output voltage to rise above the set point, the converter turns off and remains off until the voltage on FB decreases below VFB. 104 CREF Output Voltage The Si9177 is designed with an adjustable output voltage, VOUT, which is set by resistors R1 and R2, and the feedback voltage, VFB. VOUT is defined according to the following relationship: ǒ VOUT + 1 ) R1 R2 Ǔ VFB where VFB is 1.215 V. The on-time and minimum off-time are set internally to minimize ripple voltage at the maximum load current. The Si9177 has internal compensation reducing the number of required components and is designed for an inductor value of 1.5 µH and an output capacitor value of 10 µF. BYPASS Mode Si9177 can also operate in BYPASS mode to handle heavy load currents or to provide the maximum output voltage to the Document Number: 70312 S-03663—Rev. B, 07-Apr-03 The values of R1 and R2 should be kept between 5 kΩ and 100 kΩ. Power Switches The p-channel MOSFET switch is integrated in Si9177 for optimum performance and minimum overall converter size. This MOSFET is designed to minimize the gate charge loss as well as the conduction loss. The typical on-resistance is 150 mΩ with a minimum input voltage of 3.3 V. www.vishay.com 5 Si9177 New Product Vishay Siliconix DETAIL OPERATIONAL DESCRIPTION (CONT’D) An external Schottky diode is required for PSM mode operation. The Schottky diode handles the freewheeling inductor current after the p-channel MOSFET is turned off. The current rating of the Schottky is based on the maximum load current in PSM mode with the conduction time being the greatest at maximum input voltage. Combined with the maximum load current of 200 mA, the Schottky must be able to conduct 200 mA continuously. Since the forward voltage drop of the diode, VF, determines the conduction losses, select the diode with the lowest VF to maximize the converter’s efficiency. The diode should also be selected for fast switching speed to improve efficiency. The diode must be connected from the LX pin to GND. Over Temperature Protection Si9177 includes an over temperature protection circuit to prevent thermal runaway in the MOSFET switch. If the junction temperature reaches 165C, an internal soft-start capacitor is discharged, shutting down the output stage. The converter remains disabled until the junction temperature falls below 140C, allowing the converter to resume operation. TYPICAL CHARACTERISTICS (25C UNLESS NOTED) Supply Current vs. Input Voltage rDS(on) vs. Input Voltage 180 240 220 160 85 C 200 140 rDS (mW) Current (mA) PSM Mode 120 180 25 C 160 100 140 80 120 - 25 C BP Mode 100 60 2 2 3 4 5 6 3 4 Voltage (V) 6 7 Voltage (V) Efficiency vs. Load Current Switching Frequency vs. Load Current 100.00 500 VIN = 3.6 V VOUT = 3.3 V 450 VOUT = 3.0 V 95.00 400 Frequency (kHz) Efficiency (%) 5 7 90.00 VOUT = 2.2 V 85.00 80.00 350 VIN = 4.0 V 300 250 200 150 100 75.00 VIN = 6.0 V 50 70.00 0 0 50 100 150 Current (mA) www.vishay.com 6 200 250 0 50 100 150 200 Current (mA) Document Number: 70312 S-03663—Rev. B, 07-Apr-03 Si9177 New Product Vishay Siliconix TYPICAL WAVEFORMS Typical Switching Waveforms VIN = 4 V, VOUT = 2.0 V, IOUT = 100 mA Typical Switching Waveforms VIN = 4 V, VOUT = 2.0 V, IOUT = 6 mA VOUT 50 mV/div AC Coupled VOUT 50 mV/div AC Coupled VLX 2 V/div VLX 2 V/div ILX 200 mA/div ILX 200 mA/div 2 ms/div. 5 ms/div. Typical Switching Waveforms VIN = 4 V, VOUT = 2.0 V, IOUT = 200 mA Load Transient VIN = 4 V, VOUT = 2.0 V VOUT 50 mV/div AC Coupled VOUT 100 mV/div AC Coupled VLX 2 V/div ILX 200 mA/div 0.5 ms/div. 100 ms/div. Start-Up VIN = 4 V, VOUT = 2.0 V, IOUT = 100 mA VENABLE = VIN 50 ms/div. Document Number: 70312 S-03663—Rev. B, 07-Apr-03 IOUT 100 mA/div Start-Up from Disable VIN = 4 V, VOUT = 2.0 V, IOUT = 100 mA VIN 2 V/div VENABLE 2 V/div VOUT 1 V/div VOUT 1 V/div 50 ms/div. www.vishay.com 7 Si9177 Vishay Siliconix New Product TYPICAL WAVEFORMS Start-Up in Bypass Mode VIN = 4 V, IOUT = 100 mA VENABLE, BP = VIN VIN 2 V/div VOUT 2 V/div 50 ms/div. www.vishay.com 8 Document Number: 70312 S-03663—Rev. B, 07-Apr-03 This datasheet has been download from: www.datasheetcatalog.com Datasheets for electronics components.