L5983TR STMicroelectronics, L5983TR Datasheet

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Features ■ 1 output current ■ 2 input voltage ■ Output voltage adjustable from 0.6 V ■ 250 kHz switching frequency, programmable MHz ■ Internal soft-start ■ Inhibit ■ Low dropout ...

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Contents Contents 1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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L5983 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) 1.2 Pin description Table 1. Pin description N. Type 1 OUT 2 SYNCH 3 INH 4 COMP GND 8 V OUT ...

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Maximum ratings 2 Maximum ratings 2.1 Absolute maximum ratings Table 2. Absolute maximum ratings Symbol Vcc OUT F , COMP, SYNCH SW INH FB P TOT stg 2.2 Thermal data Table 3. Thermal data Symbol R thJA ...

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L5983 3 Electrical characteristics °C, VCC = 12 V, unless otherwise specified. J Table 4. Electrical characteristics Symbol Operating input voltage V CC range V Turn on V CCON V V UVLO hysteresis CCHYS CC R MOSFET ...

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Electrical characteristics Table 4. Electrical characteristics Symbol Error amplifier V High level output voltage CH V Low level output voltage CL I Bias source current FB I Source COMP pin O SOURCE I Sink COMP pin O SINK G Open ...

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L5983 4 Functional description The L5983 is based on a “voltage mode”, constant frequency control. The output voltage V is sensed by the feedback pin (FB), compared to an internal reference (0.6 V) OUT providing an error signal that, compared ...

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Functional description 4.1 Oscillator and synchronization Figure 4 shows the block diagram of the oscillator circuit. The internal oscillator provides a constant frequency clock. Its frequency depends on the resistor externally connect to FSW pin. In case the FSW pin ...

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L5983 Figure 5. Sawtooth: voltage and frequency feed forward; external synchronization Figure 6. Oscillator frequency versus FSW pin resistor Doc ID 13005 Rev 6 Functional description 9/37 ...

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Functional description 4.2 Soft-start The soft-start is essential to assure correct and safe start up of the step-down converter. It avoids inrush current surge and makes the output voltage increases monothonically. The soft-start is performed by a staircase ramp on ...

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L5983 4.3 Error amplifier and compensation 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 ...

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Functional description 4.4 Overcurrent protection The L5983 implements the over current protection sensing current flowing through the power MOSFET. Due to the noise created by the switching activity of the power MOSFET, the current sensing is disabled during the initial ...

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L5983 Figure 8. Over current protection strategy 4.5 Inhibit function The inhibit feature allows to put in stand-by mode the device. With INH pin higher than 1.9 V the device is disabled and the power consumption is reduced to less ...

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Application information 5 Application information 5.1 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 ...

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L5983 5.2 Inductor selection The inductance value fixes the current ripple flowing through the output capacitor. So the minimum inductance value in order to have the expected current ripple has to be selected. The rule to fix the current ripple ...

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Application information 5.3 Output capacitor selection The current in the capacitor has a triangular waveform which generates a voltage ripple across it. This ripple is due to the capacitive component (charge and discharge of the output capacitor) and the resistive ...

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L5983 5.4 Compensation network The compensation network has to assure stability and good dynamic performance. The loop of the L5983 is based on the voltage mode control. The error amplifier is a voltage operational amplifier with high bandwidth. So selecting ...

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Application information Equation 15 As seen in Chapter 4.3 following paragraph the guidelines to select the Type II and Type III compensation network are illustrated. Figure 9. Error amplifier, PWM modulator and LC output filter V V REF REF FB ...

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L5983 Figure 10. Type III compensation network In Figure 11 the Bode diagram of the PWM and LC filter transfer function (G and the open loop gain (G Figure 11. Open loop gain: module Bode diagram The guidelines for positioning ...

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Application information Equation 19 4. Calculate C 5 Equation 20 5. Set also the first pole at four times the system bandwidth and also the second zero at the output filter double pole: Equation 21 The suggested maximum system bandwidth ...

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L5983 Figure 12. Open loop gain Bode diagram with ceramic output capacitor Doc ID 13005 Rev 6 Application information 21/37 ...

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Application information 5.4.2 Type II compensation network If the equivalent series resistance (ESR) of the output capacitor introduces a zero with a frequency lower than the desired bandwidth (that is: 2π * ESR * C helps stabilize the loop. Electrolytic ...

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L5983 Figure 14. Open loop gain: module Bode diagram The guidelines for positioning the poles and the zeroes and for calculating the component values can be summarized as follow: 1. Choose a value for R and C5 not comparable with ...

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Application information Equation 25 For example with V ESR = 50 mΩ, the type II compensation network is: In Figure 15 is shown the module and phase of the open loop gain. The bandwidth is about 30 kHz and the ...

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L5983 Figure 15. Open loop gain Bode diagram with electrolytic/tantalum output capacitor Doc ID 13005 Rev 6 Application information 25/37 ...

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Application information 5.5 Thermal considerations The thermal design is important to prevent the thermal shutdown of device if junction temperature goes above 150 °C. The three different sources of losses within the device are: a) conduction losses due to the ...

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L5983 For this device the path through the exposed pad is the one conducting the largest amount of heat. The Rth JA paragraph is about 60 °/W. Figure 16. Switching losses 5.6 Layout considerations The PC board layout of switching ...

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Application information Figure 17. Layout example 28/37 Doc ID 13005 Rev 6 L5983 ...

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... Vout=3.3V Vout=3.3V Vout=3.3V Vout=3. STPS2L25U STPS2L25U STPS2L25U STPS2L25U R1 4.99K R1 4.99K R1 4.99K R1 4.99K R3 330 R3 330 R3 330 R3 330 C3 2.2nF C3 2.2nF C3 2.2nF C3 2.2nF R2 1.1K R2 1.1K R2 1.1K R2 1.1K Description Manufacturer 10 μ MURATA 22 μ MURATA 2 220 pF nF Coilcraft STMicroelectronics 22uF 22uF 22uF 22uF 29/37 ...

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Application information Figure 19. PCB layout (component side) Figure 20. PCB layout (bottom side) Figure 21. PCB layout (front side) 30/37 Doc ID 13005 Rev 6 L5983 ...

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L5983 Figure 22. Junction temperature vs output current Figure 24. Junction temperature vs output current Figure 26. Efficiency vs output current VCC=5V =250kHz 0.2 0.4 0.6 0.8 ...

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Application information Figure 28. Load regulation 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0.2 0.4 0.6 0.8 I [A] O Figure 30. Load transient: from 300 OUT OUT OUT OUT ...

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L5983 6 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: ECOPACK® is ...

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Package mechanical data Table 10. VFQFPN8 ( 1.08 mm) mechanical data Dim ddd Figure 33. Package dimensions 34/37 mm Min Typ Max 0.80 0.90 1.00 0.02 ...

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... L5983 7 Order codes Table 11. Order codes Order codes L5983 L5983TR Package VFQFPN8 ( 1.08 mm) Doc ID 13005 Rev 6 Order codes Packaging Tube Tube and reel 35/37 ...

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Revision history 8 Revision history Table 12. Document revision history Date 21-Dec-2006 16-Oct-2007 27-May-2008 16-Sep-2008 28-Jan-2009 15-Jun-2009 36/37 Revision 1 Initial release 2 Document status promoted from preliminary data to datasheet Updated: Cover page, Figure 5 on page 9, Figure ...

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... L5983 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. ...