PM6686TR STMicroelectronics, PM6686TR Datasheet
PM6686TR
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PM6686TR Summary of contents
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... PDAs, mobile devices, tablet PC or slates ■ 3-4 cells Li+ battery powered devices Table 1. Device summary Order codes PM6686 PM6686TR July 2009 current sensing Description PM6686 is a dual step-down controller specifically designed to provide extremely high efficiency conversion, with lossless current sensing technique. The constant on-time architecture ...
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Contents Contents 1 Simplified application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 Pin ...
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PM6686 9.4 Linear regulator section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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List of figures List of figures Figure 1. Simplified application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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PM6686 Figure 49. Inductor current and output voltage in NA SKIP mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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Simplified application schematic 1 Simplified application schematic Figure 1. Simplified application schematic 6/50 Doc ID 15281 Rev 4 PM6686 ...
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PM6686 2 Pin settings 2.1 Connections Figure 2. Pin connection (through top view) 2.2 Pin descriptions Table 2. Pin descriptions N° Pin 1 VREF2 2 TON 3 VCC 4 EN_LDO 5 VREF3 6 VIN Internal 2 V high accuracy voltage ...
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Pin settings Table 2. Pin descriptions (continued) N° Pin 7 LDO 8 LDOREFIN 9 LDO_SW 10 OUT1 11 FB1 12 ILIM1 13 PG1 14 EN1 15 HGATE1 16 PHASE1 17 BOOT1 18 LGATE1 19 PVCC 8/50 Linear regulator output. It ...
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PM6686 Table 2. Pin descriptions (continued) N° Pin 20 CP_FB 21 GND 22 PGND 23 LGATE2 24 BOOT2 25 PHASE2 26 HGATE2 27 EN2 28 PG2 29 SKIP 30 OUT2 31 ILIM2 32 REFIN2 The CP_FB is used to monitor ...
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Electrical data 3 Electrical data 3.1 Maximum rating Table 3. Absolute maximum ratings VIN to PGND PHASEx to PGND BOOTx to PHASEx PVCC to PGND HGATEx to PHASEx LGATEx, CP_FB to PGND VCC, ENx, SKIP, PGx, LDO, REFIN2, OUTx, VREF3, ...
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PM6686 4 Recommended operating conditions Table 5. Recommended operating conditions Symbol VIN VCC REFIN2 OUT1 ILIM LDOREFIN LDO DC output current (switchover function enabled) LDO DC output current (switchover function disabled) Recommended operating conditions Parameter Input voltage range, LDO = ...
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Electrical characteristics 5 Electrical characteristics VIN = load on LDO, OUT1, OUT2, VREF3, and VREF2. EN2 = EN1 = VCC, LDO_SW = 5 V, PVCC = 5 V, EN_LDO = Table 6. Electrical characteristics ...
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PM6686 Table 6. Electrical characteristics (continued) Symbol Parameter Linear regulator and reference LDO LDO output voltage LDO accuracy in adjustable mode LDO short circuit current (linear regulator enabled) LDO_SW LDO_SW switch on threshold LDO_SW LDO_SW hysteresis LDO_SW switch resistance VREF3 ...
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Electrical characteristics Table 6. Electrical characteristics (continued) Symbol Parameter Output undervoltage shutdown threshold Inputs and outputs FB1 FB1 logic level REFIN2 REFIN2 logic level LDOREFIN LDOREFIN logic level SKIP SKIP logic level TON TON logic level EN1,2 EN level EN_LDO ...
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PM6686 6 Typical operating characteristics (T = VCC (200 / 300 kHz), SKIP = GND (skip mode), LDOREFIN = SGND (LDO = 5 V), ON LDO_SW = OUT1, PVCC connected to LDO, V load unless specified). Measures performed on the ...
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Typical operating characteristics Figure 7. Load regulation OUT1 = Figure 9. Load regulation OUT1 = 1 Figure 11. Switching frequency vs load OUT1 = 16/50 Figure 8. = VCC ON Figure 10. ...
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PM6686 Figure 13. Section 1 line regulation OUT1 = Figure 15. Section 1 line regulation OUT1 = 1 Figure 17. Stand-by mode input battery current vs input voltage Typical operating characteristics Figure 14. Section 2 ...
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Typical operating characteristics Figure 19. PWM no load input currents vs input voltage Figure 21. NA SKIP no load input currents vs input voltage Figure 23. VREF2 load regulation 18/50 Figure 20. SKIP no load input currents vs input voltage ...
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PM6686 Figure 25. LDO = 5 V load regulation 6.1 Screen shots Typical operating characteristic (T FB1 = GND (OUT1 = 5 V), REFIN2 = VCC (OUT2 = 3.3 V), LDOREFIN = SGND (LDO = 5 V), CP_FB = floating, ...
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Typical operating characteristics Figure 28. OUT1 soft-start 8 A constant current load Figure 30. OUT1 soft-end, no load Figure 32. OUT1 soft-start, EN2 = VREF2 no loads applied 20/50 Figure 29. OUT2 soft-start loaded 8 A constant current load Figure ...
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PM6686 Figure 34. Soft-end, EN2 = VREF2 no loads applied Figure 36. Load transient 0 A/µs OUT1 = 5 V PWM mode Figure 38. Load transient 0 µs OUT1 = 1.5 V PWM mode Typical ...
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Typical operating characteristics Figure 40. Load transient 0 A/µs OUT2 = 3.3 V PWM mode Figure 42. Load transient 0 µs OUT2 = 1.05 V PWM mode 22/50 Figure 41. Load transient 0 ...
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PM6686 7 Block diagram Figure 44. Functional block diagram UVLO LDOREFIN LDO LDO_SW CP_FB BOOT1 HGATE1 PHASE1 OUT1 PVCC LGATE1 FB1 PG1 EN1 EN2 EN_LDO VIN VREF3 + VREF3 - ADJ. LINEAR REGULATOR LDO EN INT SWITCHOVER + THRESHOLD - ...
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Device description 8 Device description The PM6686 is a dual step down controller dedicated to provide logic voltages for notebook computers. It offers several operating configurations: it combines two synchronous buck controllers, an internal linear regulator (LDO), two voltage references ...
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PM6686 Figure 45. Resistor divider to configure the output voltage Where R1, R2 are the resistors of the FB1 pin divider, as shown in Figure 2. OUT2 output voltage is programmed with REFIN2 pin. Fixed output voltage ...
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Device description 8.1.2 Constant on time control (COT) PM6686 implements a pseudo-fixed frequency algorithm using the COT architecture. The two sections are completely independent with separated switching controllers (SMPS). The COT architecture bases its algorithm on the output ripple derived ...
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PM6686 The COT architecture uses a minimum off-time (T sense on the synchronous switch and to allow the charge of the bootstrap capacitor. A minimum on-time is also introduced to assure the start-up sequence. An adaptive anti-cross conduction algorithm avoids ...
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Device description 8.1.3 PWM PWM implements the continuous current mode (CCM). During T is turned on and the inductor current starts increasing. When the Ton is elapsed the high- side MOSFET is turned off and after a dead time during ...
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PM6686 8.1.4 SKIP To improve the efficiency at light load the PM6686 implements pulse skip operation mode. When SKIP pin is tied to GND the inductor current is sensed and equal to zero the synchronous MOSFET is ...
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Device description Figure 49. Inductor current and output voltage in NA SKIP mode Inductor current Output Vreg T ON 8.1.6 Gate drivers and logic supply The integrated high-current drivers allow the use of different power MOSFET. high-side driver is supplied ...
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PM6686 Figure 50. Internal supply diagram 8.1.7 Current sensing and current limit The PM6686 implements a positive valley current limit to protect the application from an overcurrent fault. Each section has an independent current limit setting. A new switching cycle ...
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Device description Figure 52. Current limit circuit block diagram ILIM RILIM Table 10. Current limit configuration Control pin ILIM1 ILIM2 A negative current control is also implemented: the low-side MOSFET is forced off when the current exceeds the negative ...
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PM6686 The section with the EN pin connected to VREF2 begins the soft-start only when the other section is in regulation (its PGOOD is high) and makes a soft-end suddenly when the other section is turned off. Figure 53. VOUT2 ...
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Monitoring and protections 9 Monitoring and protections The PM6686 controls its switching output to prevent any damage or uncontrolled working condition. The device offers also PGOOD signals to monitor the state of each switching output voltage. PGOOD is an open ...
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PM6686 9.4 Linear regulator section The PM6686 has an integrated linear regulator (LDO) that can provide an average of 100 mA typ. with a peak current of 270 mA typ. The LDO can be enabled using EN_LDO pin. If VIN ...
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Monitoring and protections 9.5 Charge pump The PM6686 can drive an external charge pump circuit whose typical application schematic is shown in the next figure. Figure 54. Charge pump application circuit COU T The charge pump works in 4 ...
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PM6686 The minimum voltage of the charge pump is: Equation 7 Where V is the minimum voltage of CP_FB pin(2V typ.). CP_FB In case the charge pump feedback is not used, leave the CP_FB pin floating or connect the pin ...
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Application information 10 Application information 10.1 External components selection 10.1.1 Inductor Once that switching frequency is defined, inductor selection depends on the desired inductor ripple current and load transient performance. Low inductance means great ripple current and could generate great ...
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PM6686 Table 14. Inductor manufacturer Manufacturer COILCRAFT COILCRAFT COILCRAFT 10.1.2 Input capacitor In a buck topology converter the current that flows into the input capacitor is a pulsed current with zero average value. The input RMS current of the two ...
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Application information Finally the output capacitor choice deeply impacts on the load transient response. Below there is a list of some capacitor manufacturers. Output capacitor manufacturer Table 16. Input capacitor manufacturer Manufacturer SANYO SANYO 10.1.4 MOSFET Logic-level MOSFETs are recommended, ...
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PM6686 Table 17. High-side MOSFET manufacturer Manufacturer ST ST The power dissipation of the low-side MOSFET is given by: Equation 17 Maximum conduction losses occur at the maximum input voltage: Equation 18 Choose a synchronous rectifier with low R fast ...
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Diode selection 11 Diode selection 11.1 Freewheeling diode A rectifier across the low-side MOSFET is recommended. The rectifier works as a voltage clamp across the synchronous rectifier and reduces the negative inductor swing during the dead time between turning the ...
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PM6686 11.3 Other important components 11.3.1 VIN filter A VIN pin low pass filter is suggested to reduce switching noise. The low pass filter is shown in the next figure: Figure 55. VIN pin filter Typical component value is: ...
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Diode selection Typical components values are µF and µF. 11.3.3 VREF2 and VREF3 capacitors 100 nF ceramic capacitor on VREF2 pin must be added to ensure noise rejection. If VREF3 ...
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PM6686 12 PCB design guidelines The layout is very important in terms of efficiency, stability and noise of the system possible to refer to the PM6686 demonstration board for a complete layout example. For good PC board layout ...
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PCB design guidelines Figure 58. Current paths, ground connection and driver traces layout 46/50 Doc ID 15281 Rev 4 PM6686 ...
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PM6686 13 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ® ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ...
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Package mechanical data Figure 59. Package dimensions 48/50 Doc ID 15281 Rev 4 PM6686 ...
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PM6686 14 Revision history Table 24. Document revision history Date 09-Jan-2009 26-Feb-2009 07-May-2009 23-Jul-2009 Revision 1 Initial release 2 Updated input voltage range in coverpage 3 Updated pin 29 description in Updated Table 3 on page 4 on page 34, ...
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