PM6685 STMicroelectronics, PM6685 Datasheet
PM6685
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... PM6685TR March 2011 Dual step-down main supply controller VFQFPN-32 (5mm x 5mm) Description PM6685 is a dual step-down controller specifically designed to provide extremely high efficiency conversion with loss-less current sensing technique. The constant on-time architecture assures fast load transient response and the embedded voltage feed-forward provides nearly constant switching frequency operation ...
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... Soft start and soft end . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.8 Gate drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.9 Reference voltage and bandgap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.10 Internal linear regulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.11 Power up sequencing and operative modes . . . . . . . . . . . . . . . . . . . . . . . 28 8 Monitoring and protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.1 Power good signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.2 Thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.3 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2/48 Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 8.4 Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.5 Design guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.6 Switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.7 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.8 Output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 8.9 Input capacitors selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 8.10 Power MOSFETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 8.11 Closing the integrator loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 9 Other parts design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 10 Design example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 10.1 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 10.2 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 10 ...
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... SHIFTER SMPS CONTROLLER STARTUP LDO3 MODE CONTROLLER SELECTOR UVLO Doc ID 11674 Rev 8 + UVLO UVLO LEVEL 5V SHIFTER SMPS CONTROLLER LDO5 LDO3 ENABLE LDO5 ENABLE TERMIC TERMIC FAULT CONTROLLER PM6685 LDO5 V5SW VCC OUT5 BOOT5 HGATE5 PHASE5 CSENSE5 COMP5 LGATE5 PGOOD5 EN5 ...
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... PM6685 2 Pin settings 2.1 Connections Figure 2. Pin connection (top view) Doc ID 11674 Rev 8 Pin settings 5/48 ...
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... If V5SW is connected to GND, the LDO5 linear regulator is always on. 5V internal regulator output. It can provide up to 100mA peak current. LDO5 pin supplies 18 LDO5 embedded low side gate drivers and an external load. 6/48 Description sensing) to set the current limit threshold. DSON Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 Table 2. Pin functions (continued) Pin Name Device input supply voltage. A bypass filter (4W and 4.7mF) between the battery and this pin is 19 VIN recommended. Current sense input for the 5V section. This pin must be connected through a resistor to the 20 CSENSE5 drain of the synchronous rectifier (R ...
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... Storage temperature range Junction operating temperature range Doc ID 11674 Rev 8 Value -0.3 to VCC + 0.3 -0 -0.3 to LDO5 + 0.3 (1) -0.3 to LDO5 + 0.3 -0 ( 0 -0.3 to 0.3 2 VIN pin ±1000 Other pins ±2000 Value 35 -40 to 150 -10 to 125 PM6685 Unit Unit °C/W °C °C ...
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... PM6685 4 Electrical characteristics V = 12V 0°C to 85°C, unless otherwise specified IN A Table 5. Electrical characteristics Symbol Parameter Supply section VIN Input voltage range Vcc IC supply voltage Turn-on voltage threshold V Turn-off voltage V5SW threshold Hysteresis Maximum operating V V5SW range LDO5 internal bootstrap Rdson ...
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... Both SMPS, 6V<Vin<28V 6V<VIN<28V, 0<I <50mA LDO5 6V< VIN < 28V, I =50mA LDO5 , LDO3_SEL tied to GND V > UVLO, I =0A LDO5 LDO3 V >5.1V, V >3.34V OUT5 OUT3 Doc ID 11674 Rev 8 PM6685 Min Typ Max Unit μA 90 100 110 - -120 mV 1685 1985 2285 780 920 ...
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... PM6685 Table 5. Electrical characteristics (continued) Symbol Parameter LDO3 linear regulator LDO3 linear output V LDO3 voltage I LDO3 current limit LDO3 High and low gate drivers HGATE Driver On- resistance LGATE Driver On- resistance PGOOD pins UVP/OVP protections OVP Over voltage threshold UVP Under voltage threshold ...
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... Middle level (2) High level (2) Always-off level (2) Bootstrap level (2) Always-on level (2) (2) ( EN3 SKIP SHDN FSEL LDO3_SEL Doc ID 11674 Rev 8 PM6685 Min Typ Max Unit 0.5 1.0 V -1.5 LDO5 V -0.8 LDO5 V 0.5 1.0 V -1.5 LDO5 V -0.8 LDO5 0.5 1.0 V -1.5 V LDO5 V -0.8 ...
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... PM6685 5 Typical operating characteristics FSEL = GND (200/300 kHz), SKIP = GND (skip mode), LDO3_SEL = VREF, V5SW = OUT5, input voltage VIN = 12 V, SHDN, EN3 and EN5 high, no load unless specified. Figure output efficiency vs load current Figure 5. PWM no load input battery vs input voltage Typical operating characteristics Figure 4 ...
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... Figure 7. Standby mode input battery current vs input voltage Figure 9. 5V switching frequency vs load current Figure 11. LDO5 vs output voltage 14/48 Figure 8. Shutdown mode input device current vs input voltage Figure 10. 3.3V switching frequency vs load current Figure 12. LDO3 vs output voltage Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 Figure 13. 5V voltage regulation vs load current Figure 15. Voltage reference vs load current Figure 17 PWM load transient Typical operating characteristics Figure 14. 3.3 V voltage regulation vs load current Figure 16. OUT5, LDO3 and LDO5 Power-Up Figure 18. 3.3 V PWM load transient Doc ID 11674 Rev 8 15/48 ...
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... Typical operating characteristics Figure 19 soft start (0.75 Figure 21 soft end (no load) Ω Figure 23 soft end (1 16/48 Ω load) Figure 20. 3.3 V soft start (0.55 Figure 22. 3.3 V soft end (no load) load) Figure 24. 3.3 V soft end (1 Doc ID 11674 Rev 8 PM6685 Ω load) Ω load) ...
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... PM6685 Figure 25 audible skip mode Typical operating characteristics Figure 26. 3 audible skip mode Doc ID 11674 Rev 8 17/48 ...
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... Application schematic 6 Application schematic Figure 27. Simplified application schematic 18/48 4 EN3 25 EN5 32 VREF 24 SKIP 3 FSEL Doc ID 11674 Rev 8 PM6685 31 VCC 18 LDO5 19 VIN ...
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... V and 3.3 V. The switching frequency of the two sections can be adjusted to approximately 200/300 kHz, 300/400 kHz or 400/500 kHz respectively. In order to maximize the efficiency at light load condition, a pulse skipping mode can be selected. The PM6685 includes also two linear regulators (LDO5 and LDO3) that allow the shutdown of the respective switching sections in low consumption status ...
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... The other output are unloaded. 20/ OUT OUT × OUT SMPS 5V Frequency K ON 212kHz 4,7µs 323kHz 3µs 432kHz 2.31µs =12 V, operation mode = PWM and I in Doc ID 11674 Rev 8 SMPS 3.3V Frequency 297,6kHz 3.36µs 400kHz 2.5µs 500kHz 2.0µs load PM6685 ...
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... A minimum on-time(150 ns typ) is also introduced to assure the start-up switching sequence. PM6685 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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... INT CINT V = ILOAD ( SKIP ) Doc ID 11674 Rev 8 I=gm (V1 -Vr) I=gm (V1 -Vr PWM PWM PWM PWM rator rator Co mp arator Co mp arator RFb2 RFb2 RFb2 RFb2 and the output ripple fixed Ton begins r − V × IN OUT T ON × PM6685 ensures INT ...
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... PM6685 Figure 31. PWM and pulse skip mode inductor current 7.5 No-audible skip mode If SKIP pin is tied to V kHz is enabled. At light load condition, If there is not a new switching cycle within a 30 µs (typ.) period, a no-audible skip mode cycle begins. Figure 32. Frequency clamp skip mode The low side switch is turned on until the output voltage crosses about Vreg+1% ...
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... Being fixed the valley threshold, the greater the current ripple is, greater the DC output current is 24/48 sensing technique current source ( connected CSENSE . If the voltage across the sensing element is greater than this CSENSE = I (max) I LOAD Lvalley Doc ID 11674 Rev 8 pin and determines SENSE Δ Figure 34 on page PM6685 24: ...
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... Lvalley Where RSNS is the sensing element (R PM6685 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 ...
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... The power dissipation of the drivers is a function of the total gate charge Qg of the external power MOSFETs and of the switching frequency, as shown in the following equation: Where V is the 5 V driver supply. driver 26/48 = × × driver driver g sw Doc ID 11674 Rev 8 PM6685 ...
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... Internal linear regulators The PM6685 has two linear regulators providing respectively 5 V(LDO5) and 3.3 V(LDO3) 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). Both linear regulators can provide an average output current and a peak output current of 100 mA. Bypass both LDO5 and LDO3 outputs with a minimum 1 μ ...
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... Switching regulators are enabled; internal linear regulators outputs are enabled. Internal Linear regulators active (LDO5 is always on while LDO3 depends on LDO3_SEL pin). In Standby mode LGATE5/LGATE3 pins are forced high while HGATE5/HGATE3 pins are forced low. All circuits off. Doc ID 11674 Rev 8 PM6685 Description ...
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... Thermal protection The PM6685 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. ...
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... LGATE5/LGATE3 is forced high after the soft end mode, LDO5 remains active. Exit by a power on reset or toggling SHDN or EN5/EN3 All circuitry off. Exit by a POR on VIN or toggling > +150°C SHDN. − OUT L × Δ Doc ID 11674 Rev 8 Description V × OUT V IN PM6685 ...
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... PM6685 where fsw is the switching frequency, VIN is the input voltage, VOUT is the output voltage and ΔIL is the selected inductor ripple current. In order to prevent overtemperature working conditions, inductor must be able to provide an RMS current greater than the maximum RMS inductor current ILRMS: Equation 11 Where Δ ...
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... TAYIO YUDEN TDK 32/48 Capacitor value Series (μF) POSCAP 150 to 330 TPB,TPD SPCAP UD, UE 150 to 220 = × × − CinRMS Series UMK325BJ106KM-T10 GMK325BJ106MN C3225X5R1E106M Doc ID 11674 Rev 8 ESR max (mΩ) Rated voltage ( 6 6 × × − Capacitor value Rated voltage (V) (μ PM6685 ...
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... PM6685 8.10 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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... STPS1L30M 0.34 STPS1L20M 0.37 Doc ID 11674 Rev 8 ⎞ ⎟ × OUT 2 I (max) ⎟ LOAD ⎠ max Rated reverse voltage (V) 0.047 30 0.011 30 Rated reverse Gate charge (nC) voltage ( Rated reverse Reverse current voltage (V) 30 0.00039 20 0.000075 Figure usually enough to PM6685 30 60 (uA) ...
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... PM6685 Figure 36. Circuitry for output ripple compensation The stability of the system depends firstly on the output capacitor zero frequency. The following condition should be satisfied: Equation 21 where design parameter greater than 3 and Rout is the ESR of the output capacitor. It determinates the minimum integrator capacitor value CINT: Equation 22 where gm=50us is the integrator transconductance ...
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... A good trade-off is to design the network in order to achieve an RESR given by: Equation 26 36/ INT C π × × CUT C INT C = × INT V V RIPPLE RIPPLEout + INT C INT Figure − RIPPLE R ESR Δ Doc ID 11674 Rev 8 × C INT filt + C filt = × RIPPLEout C filt . R out PM6685 ...
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... PM6685 where ΔIL is the inductor current ripple and VRIPPLE is the overall ripple of the T node voltage. It should be chosen higher than approximately 30mV. The stability of the system depends firstly on the output capacitor value and on RTOT: Equation 27 The following condition should be satisfied: Equation 28 Where free design parameter greater than 3 and determines the minimum integrator ...
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... RESR = 30 mΩ. We choose CINT equations 31, 32 and Cfilt=47 pF, RINT=1.8 kΩ by eq.26,27. C=6 Eq.33. Then R=22 kΩ (eq.34) and R1=1 kΩ (eq.35). 38/48 ⎛ ⎞ 1 ⎜ ⎜ ⎟ ⎟ × R × π × ⎝ ⎠ − R × π × Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 9 Other parts design ● 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 38. VIN pin filter Typical components values are: R=3.9 Ω and C=4.7 µF. ● VCC filter A VCC low pass filter helps to reject switching commutations noise: Figure 39. Inductor current waveforms Typical components values are: R=47 Ω ...
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... The bootstrap diode D must charge the capacitor during the off time phases. The maximum rated voltage must be higher than VINmax. A resistor RBOOT on the BOOT pin could be added in order to reduce noise when the phase node rises up, working like a gate resistor for the turn on phase of the high side MOSFET. 40/48 Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 10 Design example The following design example considers an input voltage from The two switching outputs must deliver a maximum current of 5A. The selected switching frequencies are 200 kHz for the 5 V section and 300 kHz for the 3.3 V section. 10.1 Inductor selection OUT5 60% ripple current ...
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... Lvalley LOAD . ≡ ⋅ CSENSE μ 100 A Δ I (min) = − (min) I (max) Lvalley LOAD . ≡ ⋅ CSENSE μ 100 A calculation) DSon ) = 1 kΩ INT Doc ID 11674 Rev 8 PM6685 (min Ω ≈ Ω 686 calculation) DSon = . Ω ≈ Ω 681 > 3.4 A CinRMS ...
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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 PM6685 demonstration board 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) ...
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... Place the current sense traces on the bottom side. Use a dedicated connection between the switching node and the current limit resistor RCSENSE. 44/48 Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 11 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. ECOPACK trademark. Table 18. VFQFPN 5x5x1.0 32L pitch 0.50 package dimensions Dim ...
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... Package mechanical data Figure 42. VFQFPN 5x5x1.0 32L pitch 0.50 package drawings 46/48 Doc ID 11674 Rev 8 PM6685 ...
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... PM6685 12 Revision history * Table 20. Document revision history Date 17-Jan-2006 21-Apr-2006 03-May-2006 29-Jun-2006 11-Sep-2006 24-Oct-2006 18-Oct-2007 30-Mar-2011 Revision 1 Initial release 2 Few updates 3 Graphical updates 4 Mechanical data updated Changes electrical characteristics, added COMP value skip 5 mode, pin out updated 6 Order code table updated ...
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... Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 48/48 Please Read Carefully: © 2011 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com Doc ID 11674 Rev 8 PM6685 ...