PM6680 STMicroelectronics, PM6680 Datasheet
PM6680
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PM6680 Summary of contents
Page 1
... DC voltage error due to the output ripple. Pulse skipping technique increases efficiency at very light load. Moreover a minimum switching frequency of 33kHz is selectable to avoid audio noise issues. The PM6680 provides a selectable switching frequency, allowing three different values of switching frequencies for the two switching sections. The output voltages OUT1 and OUT2 can be adjusted from 0 ...
Page 2
... Soft start and soft end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.8 Gate drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.9 Reference voltage and bandgap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.10 Internal linear regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.11 Power up sequencing and operative modes . . . . . . . . . . . . . . . . . . . . . . . 28 7.12 Monitoring and protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7.12.1 7.12.2 7.12.3 7.12.4 2/49 Power good signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 PM6680 ...
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... PM6680 7.13 Design guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 7.13.1 7.13.2 7.13.3 7.13.4 7.13.5 7.13.6 7.13.7 7.13.8 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Input capacitors selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Power MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Closing the integrator loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Other parts design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Design example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Contents 3/49 ...
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... Current waveforms in current limit conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 35. Soft start waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure 36. Circuitry for output ripple compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Figure 37. Virtual ESR network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Figure 38. VIN pin filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Figure 39. Inductor current waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure 40. Bootstrap circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure 41. Current paths, ground connection and driver traces layout . . . . . . . . . . . . . . . . . . . . . . . . 44 Figure 42. Package dimensions 4/49 PM6680 ...
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... PM6680 List of tables Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table 2. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 3. Thermal data Table 4. Pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Table 5. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 6. FSEL pin selection: typical switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Table 7. V5SW multifunction pin Table 8. Operatives modes Table 9. Protections and operatives modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Table 10. Inductor manufacturer Table 11 ...
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... Simplified application schematic 1 Simplified application schematic Figure 1. Simplified application schematic 6/49 VIN 19 LDO5 18 VCC 31 PM6680 FSEL 3 SKIP 24 VREF 32 EN1 25 EN2 4 ...
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... PM6680 2 Electrical data 2.1 Maximum rating Table 2. Absolute maximum ratings V5SW, LDO5 to PGND VIN to PGND HGATEx and BOOTx, to PHASEx PHASEx to PGND CSENSEx , to PGND CSENSEx to BOOTx LGATEx to PGND FBx, COMPx, SKIP, , FSEL,VREF to SGND1,SGND2 PGND to SGND1,SGND2 SHDN,PGOODx, OUTx, VCC, ENx to SGND1,SGND2 Power dissipation at T Maximum withstanding voltage range test condition: CDF-AEC-Q100-002- “ ...
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... Pin settings 3 Pin settings 3.1 Connections Figure 2. Pin connection (Through top view) 8/49 PM6680 PM6680 ...
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... PM6680 3.2 Functions Table 4. Pin functions N° Pin 1 SGND1 2 COMP2 3 FSEL 4 EN2 5 SHDN FB2 8 OUT2 9 BOOT2 10 HGATE2 11 PHASE2 12 CSENSE2 13 LGATE2 14 PGND 15 LGATE1 Signal ground. Reference for internal logic circuitry. It must be connected to the signal ground plan of the power supply. The signal ground plan and the power ground plan must be connected together in one point near the PGND pin ...
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... Power Good output signal for the section 2. This pin is an open drain output and when the output of the switching section 2 is out of +/- its nominal value.It is pulled down. Feedback input for the switching section 1. This pin is connected to a resistive voltage-divider from OUT1 to PGND to adjust the output voltage from 0 5.5 V. Function PM6680 ...
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... PM6680 Table 4. Pin functions (continued) N° Pin 29 OUT1 30 COMP1 31 VCC 32 VREF Output voltage sense for the switching section 1.This pin must be directly connected to the output voltage of the switching section. DC voltage error compensation pin for the switching section 1. Device Supply Voltage pin. It supplies all the internal analog circuitry except the gate drivers (see LDO5) ...
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... Fixed negative current limit threshold 12/49 Test condition Vout = Vref, LDO5 in regulation V5SW > 4.9 FBx > VREF, Vref in regulation, V5WS SHDN connected to GND, IN ENx to GND, V5SW to GND IN VCSENSE-VPGND PGND PHASE PGND PHASE PM6680 (1) Min Typ Max Unit 5.5 28 4.5 5.5 4.8 4.9 4.6 4. 5.5 1 ...
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... PM6680 Table 5. Electrical characteristics (continued ° °C, unless otherwise specified IN A Symbol Parameter On time pulse width Ton On time duration OFF time T Minimum off time OFFMIN Voltage reference Voltage accuracy Load regulation V REF Undervoltage lockout fault threshold Integrator FB Voltage accuracy FB Input bias current ...
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... V PGOOD1,2 ISink = 4 mA (3) Low level (3) Middle level (3) High level V LDO5 (3) (3) (3) V LDO5 EN1 SKIP SHDN FSEL PM6680 Min Typ Max Unit Ω 2.0 3 Ω 1.6 2.7 Ω 1.4 2.1 Ω 0.8 1.2 112 116 120 % 107 110 113 ...
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... PM6680 5 Typical operating characteristics FSEL = GND (200/300 kHz), SKIP = GND (skip mode), V5SW = V5SW = EXT5V (external 5 V power supply connected), input voltage VIN = 12 V, SHDN, EN1 and EN2 high, OUT1 = 1.5 V, OUT2 = 1. load unless specified) Figure 3. 1.5 V output efficiency vs load current Figure 5 ...
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... No-audible skip no load battery current vs input voltage Figure 9. Shutdown mode input battery current vs input voltage Figure 11. 1.05 V switching frequency vs load current 16/49 Figure 8. Stand-by mode input battery current vs input voltage Figure 10. 1.5 V switching frequency vs load current Figure 12. LDO5 vs output current PM6680 ...
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... PM6680 Figure 13. 1.5 V voltage regulation vs load current Figure 15. Voltage reference vs load current Figure 17. 1.5 V load transient Typical operating characteristics Figure 14. 1.05 V voltage regulation vs load current Figure 16. OUT1, OUT2 and LDO5 power-up Figure 18. 1.05 V load transient 17/49 ...
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... Typical operating characteristics Figure 19. 1.5 V soft start (0.25 Figure 21. 1.5 V soft end (No load) Figure 23. 1.5 V soft end (1 18/49 Ω load) Figure 20. 1.05 V soft start (0.175 Figure 22. 1.05 V soft end (No load) Ω Load) Figure 24. 1.05 V soft end (1 PM6680 Ω load) Ω Load) ...
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... PM6680 Figure 25. 1.5 V no-audible skip mode Typical operating characteristics Figure 26. 1.05 V no-audible skip mode 19/49 ...
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... REGULATOR LDO5 ENABLE SELECTOR LEVEL OUT2 SHIFTER SMPS CONTROLLER STARTUP CONTROLLER UVLO + UVLO UVLO LEVEL OUT1 SHIFTER SMPS CONTROLLER LDO5 LDO5 ENABLE TERMIC TERMIC FAULT CONTROLLER PM6680 LDO5 V5SW FB1 VCC OUT1 BOOT1 HGATE1 PHASE1 CSENSE1 COMP1 LGATE1 PGOOD1 EN1 ...
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... In order to maximize the efficiency at light load condition, a pulse skipping mode can be selected. The PM6680 includes also linear regulator (LDO5) that can power the switching drivers. If the output OUT1 regulates order to maximize the efficiency in higher consumption status, the linear regulator can be turned off and their outputs can be supplied directly from the switching outputs ...
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... Standard switching frequency values can be selected for both sections by pin FSEL as shown in the following table: Table 6. FSEL pin selection: typical switching frequency FSEL = GND FSEL = VREF FSEL = LDO5 22/49 V OUT D = -------------- OUT -------------- V IN ⁄ ------------------------------ - OUT × -------------- Fsw@OUT1 = 1.5 V (kHz) 200 290 390 PM6680 Fsw@OUT2 = 1.05 V (kHz) 325 425 590 ...
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... A minimum on-time (70 ns) is also introduced to assure the start-up switching sequence. PM6680 has a one-shot generator for each power section that turns on the high side MOSFET when the following conditions are satisfied simultaneously: the PWM comparator is high, the synchronous rectifier current is below the current limit threshold, and the minimum off-time has timed out ...
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... In fact when the voltage on the COMP pin DC voltage drop V is about 5 V-Vr+ 4.125 V. C INT CINT in the Design guidelines. ⎛ × OUT ⎝ In this condition, the output I=gm(V1-Vr provides an AC path for the INT Section 7.13.6: R ⎞ ------ - ⎠ PM6680 INT ...
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... PM6680 7.4 Pulse skip mode If the SKIP pin is tied to ground, the device works in skip mode. At light loads a zero-crossing comparator truncates the low-side switch on-time when the inductor current becomes negative. In this condition the section works in discontinuous conduction mode. The threshold between continuous and discontinuous conduction mode ...
Page 26
... MOSFET the current flowing through it is sensed. The current-sensing element is the low side MOSFET on-resistance ( Figure 33. RDSON sensing technique 26/49 Inductor current No audible skip mode ∼30us 0 Low side HS Rcsense LS RDS Time Figure 33 ). HGATE PHASE CSENSE LGATE on PM6680 ...
Page 27
... PM6680 An internal 100 µA current source is connected to CSENSE pin and determines a voltage drop on R CSENSE drop, the controller doesn't initiate a new cycle. A new cycle starts only when the sensed current goes below the current limit. Since the current limit circuit is a valley current limit, the actual peak current limit is greater than the current limit threshold by an amount equal to the inductor ripple current ...
Page 28
... Device description Where RSNS is the sensing element (R PM6680 provides also a fixed negative peak current limit to prevent an excessive reverse inductor current when the switching section sinks current from the load in PWM mode. This negative current limit threshold is measured between PHASE and SGND pins, comparing the magnitude drop on the PHASE node during the conduction time of the low side MOSFET with an internal fixed voltage of 120 mV ...
Page 29
... PM6680 When a switching section is turned off (EN1/EN2 pins low), the controller enters in soft end mode.The output capacitor is discharged through an internal 18 Ω P-MOSFET switch; when the output voltage reaches 0.3 V, the low-side MOSFET turns on, keeping the output to ground. The soft end time also depends on load condition. ...
Page 30
... Internal linear regulator The PM6680 has an internal linear regulator providing 5 V (LDO5) at ±2 % accuracy. High side drivers, low side drivers and most of internal circuitry are supplied by LDO5 output through VCC pin (an external RC filter may be applied between LDO5 and VCC). The linear regulator can provide an average output current and a peak output current of 100mA. Bypass LDO5 output with a minimum 1 µ ...
Page 31
... Thermal protection The PM6680 has a thermal protection to preserve the device from overheating. The thermal shutdown occurs when the die temperature goes above +150 °C. In this case all internal circuitry is turned off and the power sections are turned off after the discharge mode. ...
Page 32
... Where ∆I (max) is the maximum ripple current: L 32/49 to the AC adapter voltage, V INmax. ). − OUT L × ∆ the input voltage (max)) LRMS LOAD LOAD(max) (max). The maximum ∆I LOAD V × OUT the output voltage and OUT : LRMS ∆ (max PM6680 . pin SEL L L ...
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... PM6680 Equation 14 If hard saturation inductors are used, the inductor saturation current should be much greater than the maximum inductor peak current I Equation 15 Using soft saturation inductors it's possible to choose inductors with saturation current limit nearly to Ipeak. Below there is a list of some inductor manufacturers. ...
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... Below there is a list of some ceramic capacitor manufacturers. Table 12. Input capacitor manufacturer Manufacturer TAYIO YUDEN TAYIO YUDEN TDK 34/49 Capacitor value (uF) 100 to 470 100 to 470 = × × − CinRMS Series Capacitor value (uF) UMK325BJ106KM-T GMK325BJ106MN C3225X5R1E106M PM6680 ESR max (mΩ) Rated voltage (V) 2 × × − Rated voltage ( ...
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... PM6680 7.13.5 Power MOSFETs Logic-level MOSFETs are recommended, since low side and high side gate drivers are powered by LDO5. Their breakdown voltage VBR In notebook applications, power management efficiency is a high level requirement. The power dissipation on the power switches becomes an important factor in switching selections ...
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... STS4DNF60L 65 Forward Series voltage (V) STPS1L30M 0.34 STPS1L20M 0.37 ⎞ ⎟ × (max) ⎟ LOAD ⎠ max ). RSS C RSS Rated reverse voltage ( 0.047 30 0.011 30 Rated reverse Gate charge (nC) voltage ( minimum recovery INmax Rated reverse Reverse current voltage (V) (uA) 30 0.00039 20 0.000075 PM6680 30 60 ...
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... PM6680 7.13.6 Closing the integrator loop The design of external feedback network depends on the output voltage ripple. If the ripple is higher than approximately 30 mV, the feedback network ( keep the loop stable. Figure 36. Circuitry for output ripple compensation OUTPUT VOLTAGE The stability of the system depends firstly on the output capacitor zero frequency. The ...
Page 38
... CUT 1 × × INT filt + C C INT filt C = × INT RIPPLEout C filt . ? COMP COMP COMP COMP - - Comparator Comparator Comparator Comparator INT INT INT INT + + OUT OUT OUT OUT PM6680 , realize a INT PWM PWM PWM PWM ...
Page 39
... PM6680 The T node voltage is the sum of the output voltage and the triangular waveform generated by the virtual ESR network. In fact the virtual ESR network behaves like a further equivalent ESR R . ESR A good trade-off is to design the network in order to achieve an R Equation 28 where ∆I ...
Page 40
... R ⎝ − 290 kHz 2.5 uH, C out = 12mW. We choose C = 1nF by equations 30, 33 and C INT R R Input C C voltage × C ⎞ 1 ⎟ ⎟ × π × f ⎠ × π × ≈ = 330 uF with R 12 mΩ. out filt PM6680 = 47 pF, ...
Page 41
... PM6680 Figure 39. Inductor current waveforms Typical components values are: R=47 Ω and uF. ● VREF capacitor 100 nF ceramic capacitor on VREF pin must be added to ensure noise rejection. ● LDO5 output capacitors Bypass the output of each linear regulator with 1 uF ceramic capacitor closer to the LDO pin and a 4.7 uF tantalum capacitor (ESR = 2 Ω ...
Page 42
... Low side: STS12NH3LL 4. Current limit OUT1: Equation 38 42/49 Table 7 on page ripple current. ⋅ − ⋅ ⋅ 290 KHz = ripple current. ⋅ − ⋅ ⋅ 425 KHz (min) I (max) Lvalley LOAD ≈ µ ⋅ ≈ µ ⋅ ∆ I (min) − PM6680 ...
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... Layout guidelines The layout is very important in terms of efficiency, stability and noise of the system possible to refer to the PM6680 demoboard for a complete layout example. For good PC board layout follows these guidelines: ● Place on the top side all the power components (inductors, input and output capacitors, MOSFETs and diodes) ...
Page 44
... Vref. Place their output filtering capacitors as near as possible to the device. ● Place input filtering capacitors near VCC and VIN pins. ● It would be better if the feedback networks connected to COMP, FB and OUT pins are "referred" 44/49 in the same point as reference voltage V GND PM6680 Figure avoid capacitive ref ...
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... PM6680 coupling place these traces as far as possible from the gate drivers and phase (switching) paths. ● Place the current sense traces on the bottom side. If low side MOSFET R is enabled, use a dedicated connection between the switching node and the current limit resistor R ...
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... See exposed pad variations 4.85 See exposed pad variations 0.3 (1)(2) D2 Typ Max 3.10 3.20 Databook (mm) Typ Max 0.9 1 0.02 0.05 0.2 0.25 0.3 5 5.15 (2) 5 5.15 (2) 0.5 0.4 0.5 0.05 E2 Min Typ 2.90 3.10 PM6680 ® Max 3.20 ...
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... PM6680 Figure 42. Package dimensions Package mechanical data 47/49 ...
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... Mechanical data updated 4 Application schematic updated Changes electrical characteristics, added COMP value skip mode, 5 Order code table updated 6 Updated: Current sensing option and Absolute Maximum Ratings Updated: Table 1 on page 7 Section 4 on page 12 Changes Figure 27 on page 16 1, Table 3 on page 7, PM6680 ...
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... PM6680 Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. ...