LM2852YMXAX-1.0

LM2852 www.ti.com SNVS325D – JANUARY 2005 – REVISED APRIL 2013 LM2852 2A 500/1500kHz Synchronous SIMPLE SWITCHER® Buck Regulator Check for Samples: LM2852 FEATURES DESCRIPTION • • The LM2852 SIMPLE SWITCHER® synchronous buck regulator is a high frequency step-down switching voltage regulator capable of driving up to a 2A load with excellent line and load regulation. The LM2852 can accept an input voltage between 2.85V and 5.5V and deliver an output voltage that is factory programmable from 0.8V to 3.3V in 100mV increments. The LM2852 is available with a choice of two switching frequencies - 500kHz (LM2852Y) or 1.5MHz (LM2852X). It also features internal, typethree compensation to deliver a low component count solution. The exposed-pad HTSSOP-14 package enhances the thermal performance of the LM2852. 1 2 • • • • • • • Input Voltage Range of 2.85 to 5.5V Factory EEPROM Set Output Voltages from 0.8V to 3.3V in 100mV Increments Maximum Load Current of 2A Voltage Mode Control Internal Type-Three Compensation Switching Frequency of 500kHz or 1.5MHz Low Standby Current of 10µA Internal 60 mΩ MOSFET Switches Standard Voltage Options 0.8/1.0/1.2/1.5/1.8/2.5/3.3 Volts APPLICATIONS • • • • Low Voltage Point of Load Regulation Local Solution for FPGA/DSP/ASIC Core Power Broadband Networking and Communications Infrastructure Portable Computing Typical Application Circuit VIN = 3.3V PVIN CIN = 22 PF AVIN EN SS LM2852Y SNS VOUT = 2.5V ILOAD = 0A to 2A SW SGND PGND LO = 10 PH + CO = 100 PF CSS = 2.7 nF 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2005–2013, Texas Instruments Incorporated LM2852 SNVS325D – JANUARY 2005 – REVISED APRIL 2013 www.ti.com Figure 1. Efficiency vs ILOAD 96 PVIN = 3.3V EFFICIENCY (%) 94 92 90 88 86 84 0.1 1.0 10 ILOAD (A) Connection Diagram AVIN 1 14 SNS EN 2 13 NC SGND 3 12 NC 11 PGND LM2852 SS 4 NC 5 10 PGND PVIN 6 9 SW PVIN 7 8 SW Figure 2. 14-Pin HTSSOP – Top View See Package Number PWP0014A PIN DESCRIPTIONS AVIN (Pin 1): Chip bias input pin. This provides power to the logic of the chip. Connect to the input voltage or a separate rail. EN (Pin 2): Enable. Connect this pin to ground to disable the chip; connect to AVIN or leave floating to enable the chip; enable is internally pulled up. SGND (Pin 3): Signal ground. SS (Pin 4): Soft-start pin. Connect this pin to a small capacitor to control startup. The soft-start capacitance range is restricted to values 1 nF to 50 nF. NC (Pins 5, 12 and 13): No connect. These pins must be tied to ground or left floating in the application. PVIN (Pins 6, 7): Input supply pin. PVIN is connected to the input voltage. This rail connects to the source of the internal power PFET. SW (Pins 8, 9): Switch pin. Connect to the output inductor. PGND (Pins 10, 11): Power ground. Connect this to an internal ground plane or other large ground plane. SNS (Pin 14): Output voltage sense pin. Connect this pin to the output voltage as close to the load as possible. Exposed Pad: Connect to ground. 2 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 LM2852 www.ti.com SNVS325D – JANUARY 2005 – REVISED APRIL 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) −0.3V to 6.5V PVIN, AVIN, EN, SNS ESD Susceptibility (3) 2kV Power Dissipation Internally Limited Storage Temperature Range −65°C to +150°C Maximum Junction Temp. 14-Pin Exposed Pad HTSSOP Package 150°C Infrared (15 sec) 220°C Vapor Phase (60 sec) 215°C Soldering (10 sec) (1) (2) (3) 260°C Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is intended to be functional, but does not ensure specfic performance limits. For ensured specifications and test conditions, see the Electrical Characteristics. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. Human body model: 1.5kΩ in series with 100pF. SW and PVIN pins are derated to 1.5kV Operating Ratings (1) PVIN to GND 1.5V to 5.5V AVIN to GND 2.85V to 5.5V −40°C to +125°C Junction Temperature θJA (1) 38°C/W Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is intended to be functional, but does not ensure specfic performance limits. For ensured specifications and test conditions, see the Electrical Characteristics. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 3 LM2852 SNVS325D – JANUARY 2005 – REVISED APRIL 2013 www.ti.com Electrical Characteristics AVIN = PVIN = 5V unless otherwise indicated under the Conditions column. Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are ensured through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Symbol Parameter Conditions Min Typ Max Units SYSTEM PARAMETERS VOUT Voltage Tolerance (1) ΔVOUT/ΔAVIN Line Regulation (1) VOUT = 0.8V option 0.782 0.818 VOUT = 1.0V option 0.9775 1.0225 VOUT = 1.2V option 1.1730 1.2270 VOUT = 1.5V option 1.4663 1.5337 VOUT = 1.8V option 1.7595 1.8405 VOUT = 2.5V option 2.4437 2.5563 VOUT = 3.0V option 2.9325 3.0675 VOUT = 3.3V option 3.2257 3.3743 V VOUT = 0.8V, 1.0V, 1.2V, 1.5V, 1.8V or 2.5V 2.85V ≤ AVIN ≤ 5.5V 0.2 0.6 % VOUT = 3.3V 3.5V ≤ AVIN ≤ 5.5V 0.2 0.6 % ΔVOUT/ΔIO Load Regulation Normal operation VON UVLO Threshold (AVIN) Rising Falling Hysteresis 8 85 mV/A 2.47 2.85 V 150 210 mV rDSON-P PFET On Resistance Isw = 2A 75 140 mΩ rDSON-N NFET On Resistance Isw = 2A 55 120 mΩ RSS Soft-start resistance ICL Peak Current Limit Threshold LM2852X 2.75 4 4.95 LM2852Y 2.25 3 3.65 Operating Current Non-switching 0.85 2 mA Shutdown Quiescent EN = 0V Current 10 25 µA RSNS Sense pin resistance 400 fosc LM2852X 1500kHz option. 1050 1500 1825 kHz LM2852Y 500kHz option. 325 500 625 kHz 100 % IQ ISD 400 kΩ A kΩ PWM Drange Duty Cycle Range 0 ENABLE CONTROL (2) VIH EN Pin Minimum High Input VIL EN Pin Maximum Low Input IEN EN Pin Pullup Current % of AVIN 75 25 EN = 0V % of AVIN 1.2 µA THERMAL CONTROLS (1) (2) 4 TSD TJ for Thermal Shutdown 165 °C TSD-HYS Hysteresis for Thermal Shutdown 10 °C VOUT measured in a non-switching, closed-loop configuration at the SNS pin. The enable pin is internally pulled up, so the LM2852 is automatically enabled unless an external enable voltage is applied. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 LM2852 www.ti.com SNVS325D – JANUARY 2005 – REVISED APRIL 2013 LM2852Y Typical Performance Characteristics (500kHz) Efficiency vs ILoad VOUT = 1.5V Efficiency vs ILoad VOUT = 2.5V 92 96 PVIN = 3.3V PVIN = 3.3V 90 94 86 84 92 EFFICIENCY (%) EFFICIENCY (%) 88 PVIN = 5.0V 82 90 PVIN = 5.0V 88 80 86 78 84 76 0.1 1.0 0.1 10 1.0 10 ILOAD (A) ILOAD (A) Figure 3. Figure 4. Efficiency vs ILoad VOUT = 3.3V Frequency vs Temperature 95 560 94 550 VIN = 3.3V PVIN = 5.0V 540 FREQUENCY (kHz) EFFICIENCY (%) 93 92 91 90 530 520 510 89 500 88 490 87 0.1 1.0 10 480 -50 VIN = 5V -25 0 25 50 75 100 125 150 TEMPERATURE (oC) ILOAD (A) Figure 5. Figure 6. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 5 LM2852 SNVS325D – JANUARY 2005 – REVISED APRIL 2013 www.ti.com LM2852X Typical Performance Characteristics (1500kHz) Efficiency vs ILoad VOUT = 1.5V Efficiency vs ILoad VOUT = 2.5V 100 85 PVIN = 3.3V PVIN = 3.3V 80 90 70 65 60 80 EFFICIENCY (%) EFFICIENCY (%) 75 PVIN = 5.0V PVIN = 5.0V 70 60 55 50 50 45 0.1 1.0 40 0.1 10 ILOAD (A) Figure 7. Figure 8. Efficiency vs ILoad VOUT = 3.3V Frequency vs Temperature 1600 85 1550 FREQUENCY (kHz) EFFICIENCY (%) 80 PVIN = 5.0V 70 65 60 1500 1450 PVIN = 5.0V 1400 1350 1300 1.0 10 1200 -50 -25 0 25 50 75 80 85 90 o TEMPERATURE ( C) ILOAD (A) Figure 9. 6 PVIN = 3.3V 1250 55 50 0.1 10 ILOAD (A) 90 75 1.0 Figure 10. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 LM2852 www.ti.com SNVS325D – JANUARY 2005 – REVISED APRIL 2013 LM2852 Typical Performance Characteristics (Both Y and X Versions) Shutdown Current vs VIN Quiescent Current (Non-Switching) vs VIN 1100 17 1000 15 125oC 900 13 o 85 C IQ (PA) IQ SHUTDOWN (PA) 125oC 11 o 800 85oC 25 C 25oC 700 9 -40oC 7 5 2.5 3 3.5 4 4.5 5 -40oC 600 500 2.5 5.5 3 3.5 4 4.5 5 5.5 VIN (V) VIN (V) Figure 11. Figure 12. NMOS Switch RDSON vs Temperature PMOS Switch RDSON vs Temperature 100 130 120 90 PFET RDSON (m:) NFET RDSON (m:) 110 80 PVIN = 3.3V 70 PVIN = 5.0V 60 PVIN = 3.3V 100 90 PVIN = 5.0V 80 70 50 60 40 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (oC) 50 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (oC) Figure 13. Figure 14. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 7 LM2852 SNVS325D – JANUARY 2005 – REVISED APRIL 2013 www.ti.com Block Diagram SGND PVIN Reference Oscillator UVLO DAC AVIN Current Limit Ramp and Clock Generator 400 k: EN Gate Drive Error Amp SS + 20 pF 200 k: 200 k: Zc1 Zc2 SW + PWM Comp PGND SNS 8 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 LM2852 www.ti.com SNVS325D – JANUARY 2005 – REVISED APRIL 2013 APPLICATIONS INFORMATION The LM2852 is a DC-DC synchronous buck regulator belonging to Texas Instrument’s SIMPLE SWITCHER family. Integration of the PWM controller, power switches and compensation network greatly reduces the component count required to implement a switching power supply. A typical application requires only four components: an input capacitor, a soft-start capacitor, an output filter capacitor and an output filter inductor. INPUT CAPACITOR (CIN) Fast switching of large currents in the buck converter places a heavy demand on the voltage source supplying PVIN. The input capacitor, CIN, supplies extra charge when the switcher needs to draw a burst of current from the supply. The RMS current rating and the voltage rating of the CIN capacitor are therefore important in the selection of CIN. The RMS current specification can be approximated by: IRMS = ILOAD D(1-D) where • D is the duty cycle, VOUT/VIN. CIN also provides filtering of the supply. (1) Trace resistance and inductance degrade the benefits of the input capacitor, so CIN should be placed very close to PVIN in the layout. A 22 µF or 47 µF ceramic capacitor is typically sufficient for CIN. In parallel with the large input capacitance a smaller capacitor may be added such as a 1µF ceramic for higher frequency filtering. SOFT-START CAPACITOR (CSS) The DAC that sets the reference voltage of the error amp sources a current through a resistor to set the reference voltage. The reference voltage is one half of the output voltage of the switcher due to the 200kΩ divider connected to the SNS pin. Upon start-up, the output voltage of the switcher tracks the reference voltage with a two to one ratio as the DAC current charges the capacitance connected to the reference voltage node. Internal capacitance of 20pF is permanently attached to the reference voltage node which is also connected to the soft-start pin, SS. Adding a soft-start capacitor externally increases the time it takes for the output voltage to reach its final level. The charging time required for the reference voltage can be estimated using the RC time constant of the DAC resistor and the capacitance connected to the SS pin. Three RC time constant periods are needed for the reference voltage to reach 95% of its final value. The actual start-up time will vary with differences in the DAC resistance and higher-order effects. If little or no soft-start capacitance is connected, then the start-up time may be determined by the time required for the current limit current to charge the output filter capacitance. The capacitor charging equation I = C ΔV/Δt can be used to estimate the start-up time in this case. For example, a part with a 3V output, a 100 µF output capacitance and a 3A current limit threshold would require a time of 100 µs: 't = C 'V 3V = 100 PF = 100 Ps I 3A (2) Since it is undesirable for the power supply to start up in current limit, a soft-start capacitor must be chosen to force the LM2852 to start up in a more controlled fashion based on the charging of the soft-start capacitance. In this example, suppose a 3 ms start time is desired. Three time constants are required for charging the soft-start capacitor to 95% of the final reference voltage. So in this case RC=1ms. The DAC resistor, R, is 400 kΩ so C can be calculated to be 2.5nF. A 2.7nF ceramic capacitor can be chosen to yield approximately a 3ms start-up time. SOFT-START CAPACITOR (CSS) AND FAULT CONDITIONS Various fault conditions such as short circuit and UVLO of the LM2852 activate internal circuitry designed to control the voltage on the soft-start capacitor. For example, during a short circuit current limit event, the output voltage typically falls to a low voltage. During this time, the soft-start voltage is forced to track the output so that once the short is removed, the LM2852 can restart gracefully from whatever voltage the output reached during the short circuit event. The range of soft-start capacitors is therefore restricted to values 1nF to 50nF. Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated Product Folder Links: LM2852 9 LM2852 SNVS325D – JANUARY 2005 – REVISED APRIL 2013 www.ti.com COMPENSATION The LM2852 provides a highly integrated solution to power supply design. The compensation of the LM2852, which is type-three, is included on-chip. The benefit to integrated compensation is straightforward, simple power supply design. Since the output filter capacitor and inductor values impact the compensation of the control loop, the range of L, C and CESR values is restricted in order to ensure stability. OUTPUT FILTER VALUES Table 1 details the recommended inductor and capacitor ranges for the LM2852 that are suggested for various typical output voltages. Values slightly different than those recommended may be used, however the phase margin of the power supply may be degraded. Table 1. Output Filter Values Frequency Option LM2852Y (500kHz) LM2852X (1500kHz) 10 VOUT (V) PVIN (V) L (µH) C (µF) CESR (mΩ) Min Max Min Max Min Max 0.8 3.3 10 15 100 220 70 200 0.8 5.0 10 15 100 120 70 200 1.0 3.3 10 15 100 180 70 200 1.0 5.0 10 15 100 180 70 200 1.2 3.3 10 15 100 180 70 200 1.2 5.0 15 22 100 120 70 200 1.5 3.3 10 15 100 120 70 200 1.5 5.0 22 22 100 120 70 200 1.8 3.3 10 15 100 120 100 200 1.8 5.0 22 33 100 120 100 200 2.5 3.3 6.8 10 68 120 95 275 2.5 5.0 15 22 68 120 95 275 3.3 5.0 15 22 68 100 100 275 0.8 3.3 0.8 5.0 1.0 3.3 1.0 5.0 1.2 3.3 1.2 5.0 1.5 3.3 1.5 5.0 1.8 3.3 1.8 5.0 2.5 3.3 2.5 5.0 3.3 5.0 The 1500kHz version is designed for ceramic output capacitors which typically have very low ESR (