EVAL5988D STMicroelectronics, EVAL5988D Datasheet

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A continuous (more than 5 A pulsed) step-down switching Features ■ output current (more than 5 pulsed) ■ Operating input voltage from 2 ■ External 1.8 V ± 2% reference voltage ■ Output ...

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Contents Contents 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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L5988D 7 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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List of table List of table Table 1. Pinout description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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L5988D List of figures Figure 1. Test application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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Description 1 Description The L5988D is a monolithic step down power switching regulator able to deliver a continuos output current the load in most of the application conditions limited only by the thermal performance (see 5 ...

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L5988D 2 Pin function Figure 2. Pin connection Table 1. Pinout description N. Name 1, 16 OUT 2, 3 VIN 4 VCC 5 SS/INH 6 COMP 7 ILIM-ADJ SYNCH 10 FSW 11 U/O/S 12 VREF 13 SGND ...

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Maximum ratings 3 Maximum ratings Table 2. Absolute maximum ratings Symbol VCC VOUT U/O/S, SS/INH, COMP, SYNCH, Fsw, ILIM-ADJ FB P tot STG 1. During the switching activity the negative peak voltage could reach -1.5 V without ...

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L5988D 4 Electrical characteristics °C unless otherwise specified Table 4. Electrical characteristic Symbol Operating input voltage V CC range High side MOSFET DS(on) resistance Low side MOSFET on ...

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Electrical characteristics Table 4. Electrical characteristic (continued) Symbol Dynamic characteristic (see figure 1) Voltage feedback in VFB regulation Error amplifier V High level output voltage OH V Low level output voltage OL I Source output current O SOURCE I Source ...

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L5988D Table 4. Electrical characteristic (continued) Symbol - UVLO 3.3 V bus TH3 - OVP latched - No sink - UVLO 3.3 V bus TH4 - OVP latched - Sink - UVLO 12 V bus TH5 - OVP not latched ...

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Functional description 5 Functional description The L5988D is based on a voltage mode control loop. Therefore the duty ratio of the internal switch is obtained through a comparison between a saw-tooth waveform (generated by an oscillator) and the output voltage ...

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L5988D Below follows a brief description of the main blocks: ● A voltage pre-regulator supplies the internal circuitry. The external 1.8 V voltage reference is supplied by this regulator. ● A voltage monitor circuit that checks the input and internal ...

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Functional description composing the VREF magnitude. The voltage biasing of the multifunction can be set accordingly to table Table 5. A/D voltage windows 1.8 V 1.575 V 1.35 V 1.125 V 0.9 V 0.675 V 0.45 V 0.225 V 0 ...

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L5988D 5.2 Oscillator and synchronization The generation of the internal saw-tooth waveform is based on the constant current charge / discharge of an internal capacitor. The current generator is designed to get a switching frequency of 400 kHz ± 10% ...

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Functional description Table 7. FSW resistor examples R1 (kΩ 110 150 220 To improve the line transient performance, the voltage feed forward is implemented by changing the slope of the sawtooth according to the input ...

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L5988D Beating frequency noise is an issue when more than one voltage rail is on the same board. A simple way to avoid this problem is to operate all the regulators at the same switching frequency. The synchronization feature of ...

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Functional description 5.3 External voltage reference An external 1.8 V regulated voltage is provided. This reference is useful to set the voltage at the multifunction pin (see 5. source current to ILIM-ADJ and FSW pins (see and 5.5.2). ...

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L5988D During normal operation the C ● HICCUP mode is triggered (see 5.5.2) ● the input voltage goes below the UVLO threshold (see 5.5.3) ● the internal temperature is over 150°C (see 5.5.4) A new SS cycle will start when ...

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Functional description Figure 10. OVP latched 20/52 Doc ID 15324 Rev 3 L5988D ...

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L5988D 5.5.2 Current limiting The current limiting feature acts in different ways depending on the operative conditions. ● In case an overcurrent detection happens after the soft-start phase, the internal logic will trigger the “HICCUP” mode. Both switches are turned ...

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Functional description Figure 11. constant current protection at extreme duty cycles Constant current protection Constant current protection during soft start time during soft start time Table 8 shows some resistor values to adjust the current limits Table 8. ILIM-ADJ resistor ...

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L5988D 5.5.4 Thermal shutdown When the junction temperature reaches 150 °C the device enters in thermal shutdown. Both MOSFETs are turned off and the soft-start capacitor is discharged with a current of 22 µA. The device doesn’t restart until the ...

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Functional description 5.7 Error amplifier The error amplifier (E/A) provides the error signal to be compared with the sawtooth to perform the pulse width modulation. Its non-inverting input is internally connected to a 0.6 V voltage reference, while its inverting ...

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L5988D 6 Application information 6.1 Input capacitor selection The capacitor connected to the input has to be capable to support the maximum input operating voltage and the maximum RMS input current required by the device. The input capacitor is subject ...

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Application information Considering η=1 this function has its maximum 0.5: Typically C is dimensioned to keep the maximum peak-peak voltage across the input filter IN in the order Table 10. Input capacitors Manufacture MURATA ...

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L5988D In the table below some inductor part numbers are listed. Table 11. Inductors Manufacturer Coilcraft Wurth Coiltronics BI SUMIDA 6.3 Output capacitor selection The current in the capacitor has a triangular waveform (with zero average value) which generates a ...

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Application information rate load transient is required by the application the output capacitor and system bandwidth have to be chosen in order to sustain load transient and to have a fast response to the transient. In the table below some ...

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L5988D The PWM modulator gain is a function of the switching frequency: The transfer function on the LC filter is given by: where: Two different kind of networks can compensate the loop depending on the output capacitor. Type II network ...

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Application information Figure 13. Type III compensation network In Figure 14 the Bode diagram of the PWM and LC filter transfer function (G and the open loop gain (G Figure 14. Open loop gain: module bode diagram The guidelines for ...

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L5988D 1. Choose a value for R 2. Choose a gain (R where K is the feed forward constant and 1/K is equals to 18. 3. Calculate Calculate Set also the fist pole at ...

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Application information Figure 15. Open loop gain bode diagram with ceramic output capacitor 32/52 Doc ID 15324 Rev 3 L5988D ...

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L5988D 6.4.2 Type II compensation network In Figure 16 the type II network is shown. Figure 16. Type II compensation network The singularities of the network are: In Figure 17 the bode diagram of the PWM and LC filter transfer ...

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Application information 1. Choose a value for R C6 not comparable with parasitic capacitance of the board. 2. Choose a gain (R Where f is the ESR zero: ESR and Vs is the saw-tooth amplitude. The voltage feed forward keeps ...

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L5988D Figure 18. Open loop gain bode diagram with high ESR output capacitor The response of the system to a load transition in terms of output voltage regulation is affected not only by the designed compensation network but it also ...

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Application information 6.5 R.M.S. current of the embedded power MOSFETs The L5988D integrates both the power elements (high side and low side) and so the power dissipation is often the bottleneck for the output current capability (refer to the estimation ...

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L5988D 6.6 Thermal considerations The thermal design is important to prevent the thermal shutdown of the device if the junction temperature goes above 150 °C. The three different sources of losses within the device are: a) conduction losses due to ...

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Application information The junction temperature T Where T is the ambient temperature and the equivalent static thermal resistance junction to ambient of the device; it can be thJA calculated as the parallel of many paths of ...

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L5988D The red trace represents the maximum power which can be taken away as calculated above, whilst the purple trace is the total internal losses consequence, given these operating conditions, the system can manage a continuos output current ...

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Application information The characterization of the thermal impedance is strictly dependent on the layout of the board. In Figure 23. the L5988D is provided. Figure 23. Measurement of the thermal impedance of the evaluation board As it can be see, ...

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L5988D HS switch delivering an impulsive extra current equal to I recharged during the conduction time of the low side by the external power supply. The golden rule is to reduce as much as possible the stray inductance of the ...

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Application information Figure 25. Bottom board layout 6.8 Application circuit In Figure 26 is shown the demonstration board application circuit working. The operating switching frequency is 400 kHz. The designed system bandwidth is 68 kHz with a the phase margin ...

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... Chip resistor 220 kΩ ± 1% Chip resistor 1.2 kΩ ± 1% Chip resistor 4.7 kΩ ± 1% Chip resistor 56 Ω ± 1% Chip resistor 4.7 kΩ ± 1% Chip resistor 5.6 R ± 1% I.C. L5988D Doc ID 15324 Rev 3 Application information = 400 kHz) SW Manufacturer Murata Murata Wurth elektronik STMicroelectronics 43/52 ...

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... Chip resistor 82 kΩ ±1% Chip resistor 560 Ω ±1% Chip resistor 1.1 kΩ±1% Chip resistor 68 Ω ± 1% Chip resistor 4.99 kΩ ±1% Chip resistor 5.6 Ω ±1% I.C. L5988D Doc ID 15324 Rev 3 = 600 kHz 600 kHz) SW Manufacturer Murata Murata Wurth elektronik STMicroelectronics L5988D ...

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L5988D 7 Typical characteristics Figure 28. Junction temperature vs OUT Figure 30. Junction temperature vs 3 OUT Figure 29. Junction temperature vs ...

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Typical characteristics Figure 32. Junction temperature vs Figure 34. Efficiency vs. output current 3 98. 3. 400 kHz IN SW ...

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L5988D Figure 36. Efficiency vs. output current V = 12v f = 250 kHz 95. 90.00 85.00 80.00 75.00 VIN=12 VOUT=1.2 250 kHz VIN=12 VOUT=1.5 250 kHz VIN=12 VOUT=1.8 250 kHz 70.00 VIN=12 VOUT=2.5 250 kHz VIN=12 VOUT=3.3 ...

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Package mechanical data 8 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 ...

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L5988D Figure 41. HTSSOP16 mechanical drawing Doc ID 15324 Rev 3 Package mechanical data 49/52 ...

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Order codes 9 Order codes Table 16. Order codes Order codes L5988D L5988DTR 50/52 Package VFQFPN8 Doc ID 15324 Rev 3 L5988D Packaging Tube tape and reel ...

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L5988D 10 Revision history Table 17. Document revision history Date 20-Jan-2009 24-Sep-2009 18-Jan-2010 Revision 1 Initial release 2 Updated: coverpage, Updated: Section 5.2 on page 3 Table 13 on page 43 Doc ID 15324 Rev 3 Revision history Changes Table ...

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