IC PWM CTLR 1PH PWRGOOD 10-DFN

L6728

Manufacturer Part NumberL6728
DescriptionIC PWM CTLR 1PH PWRGOOD 10-DFN
ManufacturerSTMicroelectronics
L6728 datasheet
 


Specifications of L6728

Pwm TypeVoltage ModeNumber Of Outputs1
Frequency - Max330kHzDuty Cycle80%
Voltage - Supply4.5 V ~ 12 VBuckYes
BoostNoFlybackNo
InvertingNoDoublerNo
DividerNoCukNo
IsolatedNoOperating Temperature-40°C ~ 125°C
Package / Case10-DFNFrequency-max330kHz
Output Voltage0.8 VOutput Current30 A
Input Voltage1.5 V to 13.2 VMounting StyleSMD/SMT
Maximum Operating Temperature+ 125 CMinimum Operating Temperature- 40 C
For Use With497-8228 - BOARD EVALUATION W/L6728497-6418 - BOARD EVAL BASED ON L6728Lead Free Status / RoHS StatusLead free / RoHS Compliant
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Features
Flexible power supply from 5 V to 12 V
Power conversion input as low as 1.5 V
0.8 V internal reference
0.8 % output voltage accuracy
High-current integrated drivers
Power Good output
Sensorless and programmable OCP across
low-side R
DS(on)
OV / UV protections
VSEN disconnection protection
Oscillator internally fixed at 300 kHz
LSless to manage pre-bias start-up
Adjustable output voltage
Disable function
Internal soft-start
DFN10 package
Applications
Memory and termination supply
Subsystem power supply (MCH, IOCH, PCI...)
CPU and DSP power supply
Distributed power supply
General DC-DC converters
Table 1.
Device summary
Order codes
L6728
L6728TR
November 2008
Single phase PWM controller with Power Good
Description
L6728 is a single-phase step-down controller with
integrated high-current drivers that provides
complete control logic and protection to realize in
a simple way general DC-DC converters by using
a compact DFN10 package.
Device flexibility allows managing conversions
with power input V
supply voltage ranging from 5 V to 12 V.
L6728 provides simple control loop with voltage
mode EA. The integrated 0.8 V reference allows
regulating output voltages with ±0.8 % accuracy
over line and temperature variations. Oscillator is
internally fixed to 300 kHz.
L6728 provides programmable dual level over
current protection as well as over and under
voltage protection. Current information is
monitored across the low-side MOSFET R
saving the use of expensive and space-
consuming sense resistors.
PGOOD output easily provides real-time
information on output voltage status, through
VSEN dedicated output monitor.
Package
DFN10
Rev 4
L6728
DFN10
as low as 1.5 V and device
IN
DS(on)
Packaging
Tube
Tape and reel
1/31
www.st.com
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L6728 Summary of contents

  • Page 1

    ... DFN10 package. Device flexibility allows managing conversions with power input V supply voltage ranging from L6728 provides simple control loop with voltage mode EA. The integrated 0.8 V reference allows regulating output voltages with ±0.8 % accuracy over line and temperature variations. Oscillator is internally fixed to 300 kHz. ...

  • Page 2

    ... Low-side-less start up (LSLess Over current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1 Over current threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9 Output voltage setting and protections . . . . . . . . . . . . . . . . . . . . . . . . 14 10 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.1 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.2 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 11 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 11.1 Inductor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 11.2 Output capacitor( 11.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2/31 L6728 ...

  • Page 3

    ... L6728 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 12.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 12.1.1 12.1.2 12.1.3 12.1.4 12.1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 13.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 13.1.1 13.1.2 13.1.3 13.1.4 13.1.5 14 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 15 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Power input (Vin Output (Vout Signal input (Vcc Test points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Board characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Power input (Vin 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 PGOOD L6728 Reference Schematic 1.2 Block diagram Figure 2. Block diagram VSEN PGOOD 4/ VCC 1 10 BOOT PGOOD 3 7 UGATE COMP / DIS ...

  • Page 5

    ... L6728 2 Pin description and connection diagrams Figure 3. Pin connection (top view) 2.1 Pin descriptions Table 2. Pins description Pin # Name 1 BOOT 2 PHASE 3 UGATE 4 LGATE / OC 5 GND 6 VCC 7 COMP / DIS 8 FB Pin description and connection diagrams Function HS driver supply. Connect through a capacitor (100 nF) to the floating node (LS-Drain) pin and provide necessary bootstrap diode from VCC ...

  • Page 6

    ... Open drain output set free after SS has finished and pulled low when VSEN is outside the relative window. Pull voltage equal or lower than VCC. If not used it can be left floating. Parameter = 25 °C A L6728 Value Unit 45 °C/W 5 °C/W 150 ° ...

  • Page 7

    ... L6728 4 Electrical specifications 4.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol VCC to GND to PHASE GND BOOT, UGATE to GND; t < 200 ns to GND V PHASE to GND; t < 200 GND LGATE FB, COMP, VSEN to GND PGOOD to GND 4.2 Electrical characteristics Table 5. Electrical characteristics ( Symbol ...

  • Page 8

    ... BOOT - PHASE = 5 V VCC = 5 V VCC = 5 V Sourced from LGATE pin, during OC setting phase. V rising LGATE/OC VSEN rising un-latch, VSEN falling VSEN falling Sourced from VSEN VSEN rising VSEN falling PGOOD L6728 Min Typ Max Unit 1.5 A Ω 1.1 1.5 A Ω 0.65 μ ...

  • Page 9

    ... PGOOD in a compact DFN10 3x3 mm. L6728 is designed to operate from supply. The output voltage can be precisely regulated to as low as 0.8 V with ±0.8 % accuracy over line and temperature variations. The switching frequency is internally set to 300 kHz. ...

  • Page 10

    ... Power dissipation L6728 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. ...

  • Page 11

    ... Low-side-less start up (LSLess) In order to avoid any kind of negative undershoot and dangerous return from the load during start-up, L6728 performs a special sequence in enabling LS driver to switch: during the soft- start phase, the LS driver results disabled (LS = OFF) until the HS starts to switch. This avoid the dangerous negative spike on the output voltage that can happen if starting over a pre-biased output ...

  • Page 12

    ... The low side R DS(on) node when LS MOSFET is turned on with the programmed OCP thresholds voltages, internally held. If the monitored voltage is bigger than these thresholds, an over current event is detected. For maximum safety and load protection, L6728 implements a dual level over current protection system: st ● 1 level threshold the user externally set threshold ...

  • Page 13

    ... L6728 8.1 Over current threshold setting L6728 allows to easily program a 1 550 mV, simply by adding a resistor (R will be automatically set accordingly. During a short period of time (about 5 ms) following VCC rising over UVLO threshold, an internal 10 µA current (I across R . This voltage drop will be sampled and internally held by the device as 1 OCSET level over current threshold ...

  • Page 14

    ... Output voltage setting and protections 9 Output voltage setting and protections L6728 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 guarantee the output regulated voltage to be within ±0.8 % tolerance over line and temperature variations (excluding output resistor divider tolerance, when present) ...

  • Page 15

    ... L6728 10 Application details 10.1 Compensation network The control loop showed in regulated to the internal reference (when present, offset resistor between FB node and GND can be neglected in control loop calculation). Error Amplifier output is compared to oscillator saw-tooth waveform to provide PWM signal to the driver section. PWM signal is then transferred to the switching node with V amplitude ...

  • Page 16

    ... C ESR OUT 1 ⋅ ⋅ ⋅ ⋅ ⋅ ⎛ ⎞ ⋅ ⋅ -------------------- - ⎝ ⎠ ⋅ ⋅ order to obtain the desired closed loop regulator bandwidth F FB ΔV 0dB OSC ⋅ ------------------ - 20log ( 20log (V /Δ OSC Log (Freq) are in the range FB L6728 ...

  • Page 17

    ... Check phase margin obtained (it should be greater than 45°) and repeat if necessary. 10.2 Layout guidelines L6728 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

    ... Figure 8. Drivers turn-on and turn-off paths LS DRIVER VCC LGATE GND 18/ UGATE C IN PHASE LGATE GND LS MOSFET GATE INT OUT LOAD close to the device and avoid OCSET HS DRIVER HS MOSFET BOOT GATE INT UGATE C GS PHASE L6728 C DS ...

  • Page 19

    ... L6728 11 Application information 11.1 Inductor design The inductance value is defined by a compromise between the dynamic response time, the efficiency, the cost and the size. The inductor has to be calculated to maintain the ripple current (ΔI ) between 20 % and the maximum output current (typ). The inductance ...

  • Page 20

    ... F OUT SW ⋅ ESR L ΔI ⋅ OUT ⋅ ------------------------------------- - ⋅ ⋅ Δ OUT L for the load appliance or V OUT ) and the duty-cycle (D) for the regulation as follow: OUT ) 1 D – /2, with D = 0.5. The losses depends on the OUT 2 ) for the load removal). L6728 OUT_C ...

  • Page 21

    ... buses and the output voltage is fixed at 1.25 V. The application can deliver an output current The switching frequency is 300 kHz. Figure 10 demonstration board (left) and components placement (right) Figure 11. L6728 - 20 A demonstration board top (left) and bottom (right) layers Figure 12. L6728 - 20 A demonstration board inner layers 20 A demonstration board ...

  • Page 22

    ... A demonstration board Figure 13 demonstration board schematic 22/31 L6728 ...

  • Page 23

    ... Resistor, 2K2, 1/16W Resistor, 3K9, 1/16W Resistor, 18K, 1/16W Resistor, 22K, 1/16W Resistor, 20K, 1/16W Inductor, 1.25 μH, T60-18, 6 turns Easymagnet AP106019006P-1R1M Diode, 1N4148 or BAT54 STD70N02L STD95NH02LT4 Controller, L6728 20 A demonstration board Description Package Radial SMD0603 SMD1206 SMD0805 SMD1206 Radial SMD0603 ...

  • Page 24

    ... PGOOD: signaling the regular functioning (active high); – VGDHS: the bootstrap diode anode; – PHASE: Phase node; – LGATE: Low-side gate pin of the device; – HGATE: High-side gate pin of the device. 12.1.5 Board characterization Figure 14 demonstration board efficiency 24/31 L6728 ...

  • Page 25

    ... buses and the output voltage is fixed at 1.25 V. The application can deliver an output current in excess The switching frequency is 300 kHz. Figure 15. L6728 - 5 A demonstration board (left) and components placement (right) Figure 16. L6728 - 5 A demonstration board top (left) and bottom (right) layers 5 A demonstration board 25/31 ...

  • Page 26

    ... A demonstration board Figure 17 demonstration board schematic 26/31 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT COMP GND L6728 ...

  • Page 27

    ... Resistor, 3R3, 1/ Resistor, 0R, 1/ Resistor, 1R8, 1 Resistor, 15R, 1/ Resistor, 2K2, 1/ Resistor, 3K9, 1/ Resistor, 4K7, 1/ Resistor, 22K, 1/ Resistor, 10K, 1/ Inductor, 2.2 μH, WURTH 744324220LF Diode, BAT54 STS9D8NH3LL Controller, L6728 5 A demonstration board Package SMD1206 SMD0603 SMD0805 SMD1206 SMD7343 SMD0603 SMD0603 SMD0603 SMD0805 SMD0603 ...

  • Page 28

    ... PGOOD: signaling the regular functioning (active high); – VGDHS: the bootstrap diode anode; – PHASE: Phase node; – LGATE: Low-side gate pin of the device; – HGATE: High-side gate pin of the device. 13.1.5 Board characterization Figure 18 demonstration board efficiency 28/31 L6728 ...

  • Page 29

    ... L6728 14 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 the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label ...

  • Page 30

    ... Revision 1 Initial release 2 Updated T value in Table 3: Thermal data on page 6 J Added Figure 11 on page 21 3 Updated Section 14 on page Figure 17 on page 26, 4 Updated Table 5 on page 7 Changes 29, coverpage, Table 6 on page Table 7 on page 27 L6728 23, ...

  • Page 31

    ... L6728 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. ...