IC CTRLR PWM 1PHASE SO-8

L6726A

Manufacturer Part NumberL6726A
DescriptionIC CTRLR PWM 1PHASE SO-8
ManufacturerSTMicroelectronics
TypeStep-Down (Buck)
L6726A datasheet
 


Specifications of L6726A

Internal Switch(s)NoSynchronous RectifierNo
Number Of Outputs1Voltage - OutputAdj to 0.8V
Frequency - Switching270kHzVoltage - Input1.5 ~ 12 V
Operating Temperature-20°C ~ 85°CMounting TypeSurface Mount
Package / Case8-SOIC (3.9mm Width)Output Current1.5 A
Input Voltage4.1 V to 13.2 VOperating Temperature Range- 40 C to + 150 C
Mounting StyleSMD/SMTFor Use With497-9046 - BOARD EVAL BASED ON L6726A497-6364 - BOARD DEMO FOR TS4995EIJT497-6259 - BOARD EVAL 1PH STPDN CONV L6726A
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
Sensorless and programmable OCP across
Low-side R
dsON
Oscillator internally fixed at 270 kHz
Programmable soft-start
Ls-less start up
Disable function
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
L6726A
L6726ATR
March 2010
Single phase PWM controller
Description
L6726A 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 ranging from 5 V to 12 V.
L6726A provides simple control loop with trans-
conductance error amplifier. The integrated 0.8 V
reference allows regulating output voltage with
±1% accuracy over line and temperature
variations. Oscillator is internally fixed to 270 kHz.
L6726A provides programmable over current
protection. Current information is monitored
across the low-side MOSFET R
use of expensive and space-consuming sense
resistors.
FB disconnection protection prevents excessive
and dangerous output voltages in case of floating
FB pin.
Package
SO-8
SO-8
Doc ID 12754 Rev 4
L6726A
SO-8
as low as 1.5 V and device
IN
saving the
dsON
Packaging
Tube
Tape and reel
1/35
www.st.com
35

L6726A Summary of contents

  • Page 1

    ... SO-8 package. Device flexibility allows managing conversions with power input V supply voltage ranging from L6726A provides simple control loop with trans- conductance error amplifier. The integrated 0.8 V reference allows regulating output voltage with ±1% accuracy over line and temperature variations. Oscillator is internally fixed to 270 kHz. ...

  • Page 2

    ... Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1.1 7.2 Feedback disconnection protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.3 Undervoltage lock out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.1 Output voltage selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.2 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.3 Soft-start time calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.4 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8.5 Embedding L6726A-based VRs… 2/35 Overcurrent threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Doc ID 12754 Rev 4 L6726A ...

  • Page 3

    ... L6726A 9 Application Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.1 Output inductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.2 Output capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 10.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 10.1.1 10.1.2 10.1.3 10.1.4 10.1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 11.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 11.1.1 11.1.2 11.1.3 11.1.4 11.1.5 12 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 13 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Power input (VIN Power output (VOUT) ...

  • Page 4

    ... Typical application circuit and block diagram 1 Typical application circuit and block diagram 1.1 Application circuit Figure 1. Typical application circuit 12V CC C DEC L6726A Reference Schematic ( 12V with Vcc > 5V 1.2 Block diagram Figure 2. Block diagram OSCILLATOR L6726A 4/ VCC BOOT UGATE COMP ...

  • Page 5

    ... COMP / DIS 8 PHASE Pins description and connection diagrams BOOT 1 UGATE 2 L6726A GND 3 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

    ... Storage temperature range STG T Junction temperature range J 1. Measured with the component mounted on a 2S2P board in free air (6 6.7 cm, 35 μm (P) and 17.5 μm (S) copper thickness). 6/35 Parameter (1) Doc ID 12754 Rev 4 L6726A Value Unit 85 °C/W 150 °C -40 to 150 °C -20 to 150 °C ...

  • Page 7

    ... L6726A 3 Electrical specifications 3.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol V to GND PHASE BOOT to GND V to PHASE UGATE to PHASE; t < 50ns to GND V to GND PHASE V to GND LGATE to GND; t < 50ns FB, COMP to GND 3.2 Electrical characteristics -20 °C to +85 °C unless otherwise specified. ...

  • Page 8

    ... OUT (1) Sourced from FB Source current Sink current From COMP pin COMP falling BOOT - PHASE = BOOT - PHASE = VCC = VCC = Sourced from LGATE pin. See Section 7.1.1 V rising LGATE/ GND PHASE Doc ID 12754 Rev 4 L6726A Min. Typ. Max. Unit - -1 100 MHz μA 360 μ ...

  • Page 9

    ... L6726A 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

    ... This mechanism allows the system to regulate even if the current is negative. Power conversion input is flexible bus or any bus that allows the conversion (See maximum duty cycle limitation and recommended operating conditions) can be chosen freely. 10/35 ), maintaining fast switching transition. dsON Doc ID 12754 Rev 4 L6726A ...

  • Page 11

    ... L6726A 5.1 Power dissipation L6726A 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 12

    ... Soft start and disable L6726A implements a soft start to smoothly charge the output filter avoiding high in-rush currents to be required from the input power supply. The device sources a 10 µA soft start current from COMP, linearly charging the compensation network capacitors. The ramping COMP voltage is compared to the oscillator triangular waveform generating PWM pulses of increasing width that charge the output capacitors ...

  • Page 13

    ... MOSFETs in a latched condition. To recover from over current protection triggered, VCC power supply must be cycled. 7.1.1 Overcurrent threshold setting L6726A allows to easily program an overcurrent threshold ranging from 550 mV, simply by adding a resistor (R During a short time following VCC rising over UVLO threshold, an internal 10µA current (I ...

  • 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 L6726A to be supplied from 5 V and 12 V busses in or-ing diode configuration. ...

  • Page 15

    ... Application details 8.1 Output voltage selection L6726A 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

    ... II compensation 0dB ESR 1 --------------------------------- - ⋅ 2π OUT 1 = ------------------------------------------- - ⋅ ⋅ 2π C ESR OUT 1 ------------------------------ ⋅ ⋅ 2π ------------------------------------------------- - ⋅ ⎛ ⎞ ⋅ ⋅ -------------------- - 2π R ⎝ ⎠ Doc ID 12754 Rev 4 L6726A . OSC ; however, for stability 20log (gm· 20log [V /ΔV ·R /( OSC Log (Freq) ...

  • Page 17

    ... L6726A Type II compensation relies on the zero introduced by the output capacitors bank to achieve stability. Thus, a needed condition to successfully apply type II compensation is (usually true when output capacitor is based on electrolytic, aluminium electrolytic or tantalum capacitor). To define compensation network components values, the below suggestions may be followed: ...

  • Page 18

    ... I startup 8.4 Layout guidelines L6726A 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. To ...

  • Page 19

    ... L6726A Connect output bulk capacitors (C inductance and resistance associated to the copper trace, also adding extra decoupling capacitors along the way to the load when this results in being far from the bulk capacitors bank. Gate traces and phase trace must be sized according to the driver RMS current delivered to the power MOSFET ...

  • Page 20

    ... Application details 8.5 Embedding L6726A-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 21

    ... L6726A 9 Application Information 9.1 Output inductor Inductor value is defined by a compromise between dynamic response, ripple, efficiency, cost and size. Usually, inductance is calculated to maintain inductor ripple current (ΔI between 20% and 30% of maximum output current. Given the switching frequency (F the input voltage (V inductance can be calculated as follows: V – ...

  • Page 22

    ... P = ESR I rms 22/35 ⋅ ESR 1 ⋅ ⋅ F OUT SW ⋅ ESR 2 OUT ⋅ ΔV L for the load removal). OUT ) and duty-cycle (D) for the regulation as follows – OUT Doc ID 12754 Rev 4 ⋅ MAX /2, when D = 0.5. Losses depend on input L6726A for – OUT ...

  • Page 23

    ... L6726A demonstration board L6726A 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. Output voltage is programmed to 1.25 V. The voltage regulator can deliver output current. The switching frequency is 270 kHz. ...

  • Page 24

    ... A demonstration board Figure 15 demonstration board inner layers 24/35 Doc ID 12754 Rev 4 L6726A ...

  • Page 25

    ... L6726A Figure 16 demonstration board schematic PHASE PHASE HSD GND GND PHASE HSD HSD Doc ID 12754 Rev demonstration board OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT PHASE FB COMP VCC_PIN 25/35 ...

  • Page 26

    ... Resistor, 1R8, 1 Resistor, 0R, 1/ Resistor, 2K2, 1/ Resistor, 3K9, 1/ Resistor, 2K, 1/ Resistor, 20K, 1/ Inductor, 1.25 μH, T60-18, 6Turns Easymagnet AP106019006P-1R1M Diode, 1N4148 or BAT54 STD70NH02LT4 STD95NH02LT4 Controller, L6726A Doc ID 12754 Rev 4 Description Package Radial SMD0603 SMD1206 SMD0805 Radial 10 x 20mm SMD0603 SMD0603 SMD0805 ...

  • Page 27

    ... L6726A 10.1 Board description 10.1.1 Power input (VIN) This is the input voltage for the power conversion. The high-side MOSFET drain is connected to this input. Supply must be compliant with VIN recommended operating conditions and capacitors rating. If VIN voltage is compliant also to VCC range listed in recommended operating conditions, it can supply also the device through R16 resistor ...

  • Page 28

    ... A demonstration board demonstration board L6726A 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 270 kHz ...

  • Page 29

    ... L6726A Figure 20 demonstration board schematic L6726A L6726A GND Doc ID 12754 Rev demonstration board OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT COMP 29/35 ...

  • Page 30

    ... MLCC, 220 nF, X7R MLCC, 2.2 nF, X7R Resistor, 1R8, 1 Resistor, 0R, 1/ Resistor, 3R3, 1/ Resistor, 2K2, 1/ Resistor, 3K9, 1/ Resistor, 820R, 1/ Inductor, 2.20 μH, Wurth 744324220LF Diode, BAT54 Mosfet, STS9D8NH3LL Controller, L6726A Doc ID 12754 Rev 4 Description Package SMD1206 SMD0603 SMD0805 SMD1206 Ω SMD7343 SMD0603 SMD0805 ...

  • Page 31

    ... L6726A 11.1.2 Power output (VOUT) This is the output voltage of the power conversion. The output voltage is programmed to 1. can be changed by replacing R13 (adjusting of compensation network may be needed). Adding R18 allows to adjust OCP threshold. 11.1.3 IC additional supply (VCC) The controller can be supplied separately from the power conversion through VCC input. In this case, to separate VCC from VIN, R16 resistor must be removed ...

  • Page 32

    ... Package mechanical data 12 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. 32/35 Doc ID 12754 Rev 4 L6726A ® ...

  • Page 33

    ... L6726A 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 (.006inch) per side. Figure 22. Package dimensions mm. Min Typ Max 1.35 1.75 0.10 0.25 1.10 1.65 0.33 0.51 0.19 0.25 4 ...

  • Page 34

    ... Table 9. Document revision history Date 16-Oct-2006 26-Oct-2006 30-Jul-2007 23-Mar-2010 34/35 Revision 1 Initial release. 2 Mechanical data dimensions updated 3 Updated Figure 1 on page Added: 4 Section 9 on page 21, Updated: Table 5 on page 7 Doc ID 12754 Rev 4 Changes 4, tables Section 10 on page 23, Section 11 on page 28 L6726A ...

  • Page 35

    ... L6726A 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. ...