IC PWM CTLR SGL PHASE SO-8

L6727

Manufacturer Part NumberL6727
DescriptionIC PWM CTLR SGL PHASE SO-8
ManufacturerSTMicroelectronics
TypeStep-Down (Buck)
L6727 datasheet
 


Specifications of L6727

Internal Switch(s)NoSynchronous RectifierNo
Number Of Outputs1Voltage - OutputAdj to 0.8V
Frequency - Switching300kHzVoltage - Input1.5 ~ 12 V
Operating Temperature-20°C ~ 85°CMounting TypeSurface Mount
Package / Case8-SOIC (3.9mm Width)Output Current1.5 A
Input Voltage- 0.3 V to + 15 VSwitching Frequency300 KHz
Operating Temperature Range- 40 C to + 150 CMounting StyleSMD/SMT
Duty Cycle (max)80 %For Use With497-8266 - BOARD EVAL BASED ON L6727497-6258 - BOARD EVAL 1PH STPDWN CONV L6727
Lead Free Status / RoHS StatusLead free / RoHS CompliantCurrent - Output-
Power - Output-  
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Feature
Flexible power supply from 5 V to 12 V
Power conversion input as low as 1.5 V
1 % output voltage accuracy
High-current integrated drivers
Adjustable output voltage
0.8 V internal reference
Simple voltage mode control loop
Sensorless and programmable OCP across
Low-side R
dsON
Oscillator internally fixed at 300 kHz
Internal Soft-start
LS-LESS to manage pre-bias start-up
Disable function
OV / UV protection
FB disconnection protection
SO-8 package
Applications
Subsystem power supply (MCH, IOCH, PCI...)
Memory and termination supply
CPU and DSP power supply
Distributed power supply
General DC / DC converters
Table 1.
Device summary
Order codes
L6727
L6727TR
March 2010
Single phase PWM controller
Description
L6727 is a single-phase step-down controller with
integrated high-current drivers that provides
complete control logic, protections and reference
voltage to realize in an easy and simple way
general DC-DC converters by using a compact
SO-8 package.
Device flexibility allows managing conversions
with power input V
supply voltage in the range of 5 V to 12 V.
L6727 provides simple control loop with voltage-
mode error-amplifier. The integrated 0.8 V
reference allows regulating output voltages with
±1 % accuracy over line and temperature
variations. Oscillator is internally fixed to 300 kHz.
L6727 provides programmable over current
protection as well as over and under voltage
protection. Current information is monitored
across the low-side MOSFET R
use of expensive and space-consuming sense
resistors while output voltage is monitored
through FB pin.
FB disconnection protection prevents excessive
and dangerous output voltages in case of floating
FB pin.
Package
SO-8
Doc ID 12933 Rev 4
L6727
SO-8
as low as 1.5 V and device
IN
saving the
dsON
Packaging
Tube
Tape and reel
1/34
www.st.com
34

L6727 Summary of contents

  • Page 1

    ... SO-8 package. Device flexibility allows managing conversions with power input V supply voltage in the range L6727 provides simple control loop with voltage- mode error-amplifier. The integrated 0.8 V reference allows regulating output voltages with ±1 % accuracy over line and temperature variations. Oscillator is internally fixed to 300 kHz. ...

  • Page 2

    ... Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1 Overcurrent threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8 Output voltage monitor and protections . . . . . . . . . . . . . . . . . . . . . . . . 14 8.1 Undervoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.2 Overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.3 Feedback disconnection protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8.4 Undervoltage lock out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9.1 Output voltage selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9.2 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2/34 Doc ID 12933 Rev 4 L6727 ...

  • Page 3

    ... L6727 9.3 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9.4 Embedding L6727-based VRs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 10 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.1 Output inductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 10.2 Output capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 11.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 11.1.1 11.1.2 11.1.3 11.1.4 11.1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 12.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 12.1.1 12.1.2 12.1.3 12.1.4 12.1.5 13 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 14 Revision history ...

  • Page 4

    ... D 1 BOOT 7 C BOOT COMP / 2 DIS / OC UGATE PHASE LGATE GND L6727 Reference Schematic (*) R not to be connected when VCC > 5V OCSET (**) Up to 12V with Vcc > 5V CONTROL LOGIC & PROTECTIONS DISABLE ERROR L6727 AMPLIFIER Doc ID 12933 Rev 1.5V to 19V (**) BULK HS gHS gLS LS ...

  • Page 5

    ... OC 8 PHASE Pins description and connection diagrams BOOT 1 8 UGATE 2 7 L6727 GND 3 6 LGATE driver supply. Connect through a capacitor (100 nF) to the floating node (LS-drain) pin and provide necessary bootstrap diode from VCC. HS driver output. Connect to HS MOSFET gate. All internal references, logic and drivers are connected to this pin. ...

  • Page 6

    ... GND to PHASE V to PHASE; t < UGATE to GND V to GND PHASE to GND V LGATE to GND; t < COMP to GND FB to GND 6/34 Parameter (1) Parameter -0 Doc ID 12933 Rev 4 L6727 Value Unit 85 °C/W 150 °C -40 to 150 °C -20 to 150 °C Value Unit -0 0.3 BOOT PHASE ...

  • Page 7

    ... L6727 3.2 Electrical characteristics = -20 °C to +85 °C, unless otherwise specified Table 5. Electrical characteristics Symbol Parameter Recommended operating conditions V Device supply voltage CC V Conversion input voltage IN Supply current and power-ON I VCC supply current CC I BOOT supply current BOOT VCC turn-ON UVLO Hysteresis ...

  • Page 8

    ... Fixed OC threshold OCTH Over and undervoltage protections OVP OVP threshold UVP UVP threshold 1. Guaranteed by design, not subject to test. 8/34 Test conditions VCC rising V to GND, VCC > V PHASE CC_OC FB rising FB falling Doc ID 12933 Rev 4 L6727 Min. Typ. Max. Unit 8 V -400 0.6 V ...

  • Page 9

    ... L6727 is designed to operate from supply bus. Thanks to the high precision 0.8V internal reference, the output voltage can be precisely regulated to as low as 0.8 V with ± ...

  • Page 10

    ... Power dissipation L6727 embeds high current MOSFET drivers for both high side and low side MOSFETs then important to consider the power that the device is going to dissipate in driving them in order to avoid overcoming the maximum junction operative temperature. Two main terms contribute in the device power dissipation: bias power and drivers' power. ...

  • Page 11

    ... Low-side-less start up (LSLess) In order to manage start up over pre-biased output, L6727 performs a special sequence in enabling LS driver to switch: during the soft-start phase, LS driver results disabled (LS = OFF) until HS starts to switch. This avoids the dangerous negative spike on the output voltage that can happen if starting over a pre-biased output ...

  • Page 12

    ... COMP / DIS pin. Setting free the pin, this current pulls it over the threshold and the device enables again performing a new SS. To disable the device, the external pull-down needs to overcome COMP output current for about 15 μs. Once disabled, COMP output current drops to 20μA. Figure 5. Start up sequence; V 12/ (Left) overcurrent hiccup (Right) CC Doc ID 12933 Rev 4 L6727 ...

  • Page 13

    ... MOSFETs for 2048 clock cycles (plus internal SS remaining time, if triggered during a SS phase); then it will begin a new soft-start. If the overcurrent condition is not removed, the continuous fault will cause L6727 to go into a hiccup mode with a typical period of 13.6 ms and very low power dissipation. ...

  • Page 14

    ... UVLO is provided: the device will start up when VCC reaches UVLO upper threshold and will shutdown when VCC drops below UVLO lower threshold. The 4.1 V maximum UVLO upper threshold allows L6727 to be supplied from 5 V and 12 V busses in or-ing diode configuration. ...

  • Page 15

    ... Application details 9.1 Output voltage selection L6727 is capable to precisely regulate an output voltage as low as 0 fact, the device comes with a fixed 0.8 V internal reference that guarantees the output regulated voltage to be within ±1 % tolerance over line and temperature variations between 0 °C and +70 °C (excluding output resistor divider tolerance, when present) ...

  • Page 16

    ... F LC ESR 1 --------------------------------- - ⋅ 2π OUT 1 = ------------------------------------------- - ⋅ ⋅ 2π C ESR OUT 1 ------------------------------ ⋅ ⋅ 2π ---------------------------------------------------- - ⋅ ⋅ 2π ------------------------------------------------- - ⋅ ⎛ ⎞ ⋅ ⋅ -------------------- - 2π R ⎝ ⎠ ------------------------------ - ⋅ ⋅ 2π Doc ID 12933 Rev 4 /R ratio, however, for 20log ( 20log (V /Δ OSC Log (Freq) L6727 ...

  • Page 17

    ... Layout guidelines L6727 provides control functions and high current integrated drivers to implement high- current step-down DC-DC converters. In this kind of application, a good layout is very important. The first priority when placing components for these applications has to be reserved to the power section, minimizing the length of each connection and loop as much as possible ...

  • Page 18

    ... LGATE GND 18/ near as possible to the load, minimizing parasitic OUT V IN UGATE C IN PHASE L6727 LGATE GND LS MOSFET GATE INT Doc ID 12933 Rev OUT LOAD close to the device and avoid OCSET in Figure 1 DRIVER HS MOSFET BOOT GATE INT UGATE PHASE PHASE L6727 Figure ...

  • Page 19

    ... L6727 9.4 Embedding L6727-based VRs When embedding the VR into the application, additional care must be taken since the whole switching DC/DC regulator and the most common system in which it has to work is a digital system such similar. In fact, latest MBs have become faster and more powerful: high speed data busses are more and more common and switching-induced noise produced by the VR can affect data integrity if additional layout guidelines are not followed ...

  • Page 20

    ... When this condition is reached, the response time is limited only by the time required to charge the inductor. Figure 10. Inductor current ripple vs output voltage 20/34 ), the output voltage (V IN OUT OUT Doc ID 12933 Rev 4 ) and the desired ripple current (ΔI L6727 ) ...

  • Page 21

    ... L6727 10.2 Output capacitors Output capacitors choice depends on the application constraints in point of output voltage ripple and output voltage deviation during a load transient. During steady-state conditions, the output voltage ripple is influenced by ESR and capacitance of the output capacitors as follows: ΔV ΔI = OUT_ESR L ΔV Δ ...

  • Page 22

    ... A demonstration board demonstration board L6727 demonstration board realizes on a four-layer PCB a step-down DC/DC converter and shows the operation of the device in a general purpose application. Input voltage can range from bus (when VCC > need to be removed). Output voltage is programmed to 1.25 V. The voltage regulator can deliver output current. The switching frequency is 300 kHz ...

  • Page 23

    ... L6727 Figure 13 demonstration board inner layers Doc ID 12933 Rev demonstration board 23/34 ...

  • Page 24

    ... A demonstration board Figure 14 demonstration board schematic PHASE PHASE HSD 24/34 GND GND PHASE HSD HSD Doc ID 12933 Rev 4 L6727 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT PHASE FB COMP VCC_PIN ...

  • Page 25

    ... Resistor, 2R2, 1 Resistor, 1R8, 1 Resistor, 0R, 1/ Resistor, 2K2, 1/ Resistor, 3K9, 1/ Resistor, 33K, 1/ Resistor, 12K, 1/ Inductor, 1.25 μH, T60-18, 6Turns Easymagnet AP106019006P-1R1M Diode, 1N4148 or BAT54 STD55NH2LL STD90NH2LL Controller, L6727 Doc ID 12933 Rev demonstration board Description Package Radial SMD0603 SMD1206 SMD0805 Radial SMD0603 SMD0603 ...

  • Page 26

    ... COMP: output of the error amplifier; – FB: inverting input of the error amplifier; – PH: Phase pin of the device; – LG: Low-Side gate pin of the device; – UG: High-Side gate pin of the device. 11.1.5 Demonstration board efficiency Figure 15 demonstration board efficiency 26/34 Doc ID 12933 Rev 4 L6727 ...

  • Page 27

    ... L6727 demonstration board L6727 demonstration board realizes on a two-layer PCB a step-down DC/DC converter and shows the operation of the device in a general-purpose low-current application. Input voltage can range from bus. Output voltage is programmed at 1.25 V. The application can deliver an output current in excess The switching frequency is 300 kHz ...

  • Page 28

    ... A demonstration board Figure 18 demonstration board schematic 28/34 L6727 L6727 GND Doc ID 12933 Rev 4 L6727 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT COMP ...

  • Page 29

    ... MLCC, 220 pF, X7R Resistor, 1R8, 1 Resistor, 0R, 1/ Resistor, 3R3, 1/ Resistor, 15R, 1/ Resistor, 2K2, 1/ Resistor, 3K9, 1/ Resistor, 4K7, 1/ Inductor, 2.20 μH, Wurth 744324220LF Diode, BAT54 Mosfet, STS9D8NH3LL Controller, L6727 Doc ID 12933 Rev demonstration board Description Package SMD1206 SMD0603 SMD0805 SMD1206 Ω SMD7343 SMD0603 ...

  • Page 30

    ... COMP: output of the error amplifier; – FB: inverting input of the error amplifier; – PH: Phase pin of the device; – LG: Low-Side gate pin of the device; – UG: High-Side gate pin of the device. 12.1.5 Demonstration board efficiency Figure 19 demonstration board efficiency 30/34 Doc ID 12933 Rev 4 L6727 ...

  • Page 31

    ... L6727 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. ECOPACK trademark. Table 8. SO-8 mechanical data Dim ( ddd 1. D and F does not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm ( ...

  • Page 32

    ... Package mechanical data Figure 20. Package dimensions 32/34 Doc ID 12933 Rev 4 L6727 ...

  • Page 33

    ... L6727 14 Revision history Table 9. Revision history Date 04-Dec-2006 28-Feb-2007 06-Jun-2007 23-Mar-2010 Revision 1 Initial release. 2 Updated V values in OCTH Updated Figure 1: Typical application circuit on page 3 Table 3 and Table 4 on page 6 Added Section 10: Application information on page 20 A demonstration board on page 4 demonstration board on page 27 Updated: ...

  • Page 34

    ... 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 34/34 Please Read Carefully: © 2010 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com Doc ID 12933 Rev 4 L6727 ...