L6726A_07

Manufacturer Part NumberL6726A_07
DescriptionSingle phase PWM controller
ManufacturerSTMICROELECTRONICS [STMicroelectronics]
L6726A_07 datasheet
 


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Feature
Flexible power supply from 5V to 12V
Power conversion input as low as 1.5V
1% output voltage accuracy
High-current integrated drivers
Adjustable output voltage
0.8V internal reference
Sensorless and programmable OCP across
Low-side R
dsON
Oscillator internally fixed at 270kHz
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 & DSP power supply
Distributed power supply
General DC / DC converters
Table 1. Device summary
Order codes
L6726A
L6726ATR
July 2007
Single phase PWM controller
SO-8
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
as low as 1.5V and device
IN
supply voltage ranging from 5V to 12V.
L6726A provides simple control loop with trans-
conductance error amplifier. The integrated 0.8V
reference allows regulating output voltage with
±1% accuracy over line and temperature
variations. Oscillator is internally fixed to 270kHz.
L6726A provides programmable over current
protection. Current information is monitored
across the Low-Side mosfet R
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
Rev 3
L6726A
saving the use
dsON
Packaging
Tube
Tape & Reel
1/24
www.st.com
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L6726A_07 Summary of contents

  • Page 1

    Feature ■ Flexible power supply from 5V to 12V ■ Power conversion input as low as 1.5V ■ 1% output voltage accuracy ■ High-current integrated drivers ■ Adjustable output voltage ■ 0.8V internal reference ■ Sensorless and programmable OCP across ...

  • Page 2

    Contents Contents 1 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 4 1.1 Application circuit . . . . . . . ...

  • Page 3

    L6726A 8 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

  • 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 (1) Up ...

  • Page 5

    L6726A 2 Pins description and connection diagrams Figure 3. Pins connection (top view) 2.1 Pin descriptions Table 2. Pins descriptions Pin n Name 1 BOOT 2 UGATE 3 GND 4 LGATE / OC 5 VCC COMP / ...

  • Page 6

    Pins description and connection diagrams 2.2 Thermal data Table 3. Thermal data Symbol R Thermal resistance junction to ambient thJA T Maximum junction temperature MAX T Storage temperature range STG T Junction temperature range J 1. Measured with the component ...

  • 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 ...

  • Page 8

    Electrical specifications Table 5. Electrical characteristics (continued 12V -20°C to +85°C unless otherwise specified Symbol Parameter Reference Output voltage accuracy Transconductance error amplifier gm Transconductance I Input bias current FB (1) A Open loop ...

  • Page 9

    L6726A 4 Device description L6726A is a single-phase PWM controller with embedded high-current drivers that provides complete control logic and protections to realize in an easy and simple way a general DC- DC step-down converter. Designed to drive N-channel MOSFETs ...

  • Page 10

    Driver section 5 Driver section The integrated high-current drivers allow using different types of power MOSFET (also multiple MOSFETs to reduce the equivalent R The driver for high-side MOSFET uses BOOT pin for supply and PHASE pin for return. The ...

  • 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 ...

  • Page 12

    Soft start and disable 6 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 10µA soft start current ...

  • Page 13

    L6726A 7 Protections 7.1 Over current protection The over current feature protects the converter from a shorted output or overload, by sensing the output current information across the Low Side MOSFET drain-source on- resistance, R dsON the use of expensive ...

  • Page 14

    Protections Figure 6. OC threshold setting procedure timings (top) and waveforms (bottom) UVLO Th VCC PWM ramp bottom edge Enable Th COMP 700mV LGATE 7.3 Under voltage lock out In order to avoid anomalous behaviors of the device when the ...

  • Page 15

    L6726A 8 Application details 8.1 Output voltage selection L6726A is capable to precisely regulate an output voltage as low as 0.8V. In fact, the device comes with a fixed 0.8V internal reference that guarantees the output regulated voltage to be ...

  • Page 16

    Application details depending on the output capacitor ESR. The DC Gain of the modulator is simply the input divided by the peak-to-peak oscillator voltage ∆V voltage scaled and transferred to FB node by the output resistor ...

  • 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 ...

  • Page 18

    Application details 8.3 Soft Start time calculation To calculate SS time ( The previous equation refers only setting phase or COMP set free to the beginning of V approximately estimated as follow: t delay Once ...

  • 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 ...

  • 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 ...

  • Page 21

    L6726A 9 Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second level interconnect is marked on the package and on ...

  • Page 22

    Package mechanical data Table 6. SO-8 mechanical data Dim ( ddd 1. D and F does not include mold flash or protrusions. Mold flash or potrusions shall not ...

  • Page 23

    L6726A 10 Revision history Table 7. Revision history Date 16-Oct-2006 26-Oct-2006 30-Jul-2007 Revision 1 Initial release. 2 Mechanical data dimensions updated 3 Updated Figure 1 on page Revision history Changes 4, tables 23/24 ...

  • Page 24

    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 ...