PM8903A

PM8903A 3 A step-down monolithic switching regulator Datasheet − production data Features ■ Integrated 35 mΩ MOSFETs for high efficiency ■ 3 A continuous output current ■ 2.8 V to 6 V input voltage (VIN) ■ 2.9 V to 5.5 V supply voltage (VCC) ■ Adjustable output voltage down to 0.6 V ■ 1% output voltage accuracy ■ 1.1 MHz switching frequency operation ■ PSKIP mode to optimize light load efficiency ■ Embedded bootstrap diode ■ Thermally compensated loss-less current sense across HS and LS MOSFETs ■ OV/UV/OC and overtemperature protection ■ Internal soft-start and soft-stop ■ Interleaving synchronization (up to 2 ICs) ■ Power Good output ■ Shutdown function (< 15 µA quiescent current) ■ VFQFPN16 3 x 3 mm compact package VFQFPN16 (3 x 3 mm) The PM8903A features low-resistance integrated nMOS and proprietary pulse-skipping mode for optimum efficiency over all the loading range. The voltage mode control loop allows the widest range of output filters. Current sense is internally thermally compensated for optimum precision. Applications ■ Subsystem power supply ■ CPU, DSP and FPGA power supplies ■ Distributed power supply ■ General DC-DC converters The integrated 0.6 V reference allows the regulation of output voltages with ±1% accuracy over temperature variations. Switching frequency is typically set to 1.1 MHz and can be programmed to 0.8 MHz or 1.0 MHz. Out of phase synchronization allows the reduction of input RMS current. The PM8903A provides precise dual-threshold overcurrent protection as well as over/undervoltage and overtemperature protection. PGOOD output easily provides realtime information on the output voltage. Description The PM8903A is a high efficiency monolithic stepdown switching regulator designed to deliver up to 3 A continuous current. The IC operates from 2.8 V to 6 V input voltage (VIN). Table 1. Device summary The PM8903A is available in VFQFPN16 3 x 3 mm. Order codes Package Packaging PM8903A VFQFPN16 (3 x 3 mm) Tube PM8903ATR VFQFPN16 (3 x 3 mm) Tape and reel January 2013 This is information on a product in full production. Doc ID 024147 Rev 1 1/33 www.st.com 33 Contents PM8903A Contents 1 2 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 3 1.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 4.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2 Recommended operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.4 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1 Power section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2 Startup and shutdown management . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3 6 Low-side-less startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2.2 Soft-off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Output voltage monitoring and protection . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3.1 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3.2 Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.3.3 Feedback disconnection protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.3.4 Power Good (PGOOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.4 Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.5 Overtemperature protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.6 Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.7 Pulse-skipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.8 Multifunction pin PSKIP/MS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1 2/33 5.2.1 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Doc ID 024147 Rev 1 PM8903A 7 Contents 6.2 Output voltage setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.3 Inductor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.4 Output capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.5 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 PM8903A demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.1 Detailed demonstration board description . . . . . . . . . . . . . . . . . . . . . . . . 24 7.1.1 Power input (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.1.2 Signal input (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.1.3 Output (VOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.1.4 Test points and jumper connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Doc ID 024147 Rev 1 3/33 Typical application circuit and block diagram 1 Typical application circuit and block diagram 1.1 Application circuit Figure 1. 1.2 Block diagram Figure 2. 4/33 Typical application circuit Block diagram Doc ID 024147 Rev 1 PM8903A PM8903A 2 Pin description and connection diagrams Pin description and connection diagrams Pin connection (top view) PGND PGND VIN VIN Figure 3. 16 15 14 13 1 12 2 11 3 10 4 9 5 6 7 8 VCC GND FB COMP PHASE PHASE PHASE PSKIP / MS EN SYNCH PGOOD BOOT 2.1 Pin description Table 2. Pin description Pin # Name Function 1 EN Enable. Internally pulled up by 5 µA to VCC. Force low to disable the device, set free or pull up above turn-on threshold to enable the converter operations. 2 SYNCH Synchronization pin. According to PSKIP status, the IC sends the synchronization signal out of this pin when master, while accepting a synchronization signal when slave. Connect to the same SYNCH pin of a similar part when synchronizing ICs. In case of single IC operation, leave floating. 3 PGOOD Open drain output set free after SS has finished and pulled low when VOUT is out of the PGOOD window or any protection is triggered. Pull up to a voltage lower than VCC, if not used it can be left floating. 4 BOOT Bootstrap pin. It provides power supply for the floating high-side driver. Connect with 0.1 µF to PHASE. See Figure 1. 5 to 7 PHASE Output inductor connection. The pins are connected to the embedded MOSFETs (high-side source and low-side drain). Connect directly to output inductor. See Figure 1. 8 Pulse-skip and master/slave definition. Connect with a resistor to GND or leave it floating to define: Pulse-skip feature status; PSKIP / MS Master/slave for synchronization; Switching frequency. See Section 5.8 on page 17. Doc ID 024147 Rev 1 5/33 Pin description and connection diagrams Table 2. 6/33 PM8903A Pin description (continued) Pin # Name Function 9 COMP 10 FB 11 GND All the internal references are referred to this pin. Connect to the PCB Signal Ground. 12 VCC Device power supply. Operative voltage is 2.9 V - 5.5 V. Filter with at least 1 µF MLCC vs. GND. 13, 14 VIN Power input voltage, connected to embedded high-side drain. Supply range is from 2.8 V to 6 V. Bypass VIN pins to PGND pins close to the IC package with high quality MLCC capacitors (at least 10 µF). See Figure 1. 15, 16 PGND Power ground connection, connected to embedded low-side MOSFET source. Connect to PGND PCB plane. See Figure 1. Thermal pad Thermal pad connects the silicon substrate and makes good thermal contact with the PCB. Connect to the PCB PGND plane. Error amplifier output. Connect with an (RF - CF) // CP to FB. See Figure 1 The device cannot be disabled by pulling low this pin. Error amplifier inverting input. Connect with RFB or RFB // (RS - CS) to VSEN and with an (RF - CF) // CP to COMP. A resistor ROS to GND sets the output voltage ratio. See Figure 1 Doc ID 024147 Rev 1 PM8903A 3 Thermal data Thermal data Table 3. Symbol Thermal data Parameter Value Unit RthJA Thermal resistance junction-to-ambient (Device soldered on standard demonstration board, see Section 7 for details) 30 °C/W RthJC Thermal resistance junction-to-case 12 °C/W TMAX Maximum junction temperature 150 °C TSTG Storage temperature range -40 to 150 °C TJ Junction temperature range -25 to 125 °C Doc ID 024147 Rev 1 7/33 Electrical specifications PM8903A 4 Electrical specifications 4.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol Parameter to PGND, GND -0.3 to 6 V VIN to PGND, GND -0.3 to 7 V VBOOT to PGND, GND to PHASE -0.3 to 13 -0.3 to 6 V VPHASE to PGND, GND to PGND, GND, VIN=6 V, t