EVALA5970AD STMicroelectronics, EVALA5970AD Datasheet

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Features ■ Qualified following the AEC-Q100 requirements (see PPAP for more details) ■ output current ■ Operating input voltage from ■ 3 (±2%) reference voltage ■ Output voltage adjustable from ...

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

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A5970AD 8.1 Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...

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Pin settings 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) 1.2 Pin description Table 1. Pin description N Pin 1 OUT 2 SYNCH 3 INH 4 COMP VREF 7 GND 8 VCC 4/42 ...

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A5970AD 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol V Input voltage 8 OUT pin DC voltage V 1 OUT pin peak voltage at Δt = 0.1 μs I Maximum output current ...

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Electrical characteristics 3 Electrical characteristics T = -40 °C to 125 °C, VCC = 12 V, unless otherwise specified. J Table 4. Electrical characteristics Symbol Operating input V CC voltage range MOSFET on R DS(on) resistance Maximum limiting I L ...

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A5970AD Table 4. Electrical characteristics (continued) Symbol High input voltage Low input voltage Slave synch current Master output amplitude Output pulse width Reference section Reference voltage Line regulation Load regulation Short circuit current 1. With °C, I ...

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Datasheet parameters over the temperature range 4 Datasheet parameters over the temperature range The 100% of the population in the production flow is tested at three different ambient temperatures (-40 °C; +25 °C, +125 °C) to guarantee the datasheet parameters ...

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A5970AD 5 Functional description The main internal blocks are shown in the device block diagram in ● A voltage regulator supplying the internal circuitry. From this regulator, a 3.3 V reference voltage is externally available. ● A voltage monitor circuit ...

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Functional description 5.2 Voltages monitor An internal block continuously senses the V their thresholds, the regulator begins operating. There is also a hysteresis on the V (UVLO). Figure 4. Internal circuit 5.3 Oscillator and synchronization Figure 5 shows the block ...

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A5970AD Figure 5. Oscillator circuit block diagram Figure 6. Synchronization example SYNCH SYNCH SYNCH A5970AD A5973D A5973D A5973D SS/INH SS/INH SS/INH SYNCH SYNCH SYNCH A5970AD A5973D A5973D A5973D SS/INH SS/INH SS/INH 5.4 Current protection The A5970AD features two types of ...

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Functional description threshold. The frequency shifter feedback voltage decreases (due to the reduced duty cycle), the switching frequency decreases also. Figure 7. Current limitation circuitry 5.5 Error amplifier The voltage error amplifier is the core of the loop regulation. It ...

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A5970AD In fact, when the current of the power element is equal to the inductor current, the diode turns OFF and the drain of the power is able to go high. But during its recovery time, the diode can be ...

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Functional description 5.8 Thermal shutdown The shutdown block generates a signal that turns OFF the power stage if the temperature of the chip goes higher than a fixed internal threshold (150±10 °C). The sensing element of the chip is very ...

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A5970AD 6 Additional features and protection 6.1 Feedback disconnection If the feedback is disconnected, the duty cycle increases towards the maximum allowed value, bringing the output voltage close to the input supply. This condition could destroy the load. To avoid ...

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Closing the loop 7 Closing the loop Figure 9. Block diagram of the loop 16/42 Doc ID 14661 Rev 4 A5970AD ...

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A5970AD 7.1 Error amplifier and compensation network The output L-C filter of a step-down converter contributes with 180 degrees phase shift in the control loop. For this reason a compensation network between the COMP pin and GROUND is added. The ...

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Closing the loop whereas the zero is defined as: Equation the low frequency which sets the bandwidth, while the zero F P1 the frequency of the double pole of the L-C filter (see below). F frequency. 7.2 ...

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A5970AD If the damping coefficient δ is very close to zero, the roots of the equation become a double root whose value is ω Similarly for A LC Equation 11 7.3 PWM comparator The PWM gain is given by the ...

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Closing the loop Example: Considering 2 265 kHz 1.3 kHz µ 2.5 kHz PLC F = 8.7 kHz ZESR Finally R = ...

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A5970AD 8 Application information 8.1 Component selection ● Input capacitor The input capacitor must be able to support the maximum input operating voltage and the maximum RMS input current. Since step-down converters draw current from the input in pulses, the ...

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Application information Where V is the freewheeling diode forward voltage and V F internal PDMOS. Considering the range D IRMS going through the input capacitor. Capacitors that can be considered are: Electrolytic capacitors: These are widely used due to their ...

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A5970AD Table 7. Output capacitor selection Manufacturer (1) Sanyo POSCAP AVX KEMET Sprague 1. POSCAP capacitors have some characteristics which are very similar to tantalum. ● Inductor The inductor value is very important as it fixes the ripple current flowing ...

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Application information 8.2 Layout considerations The layout of switching DC-DC converters is very important to minimize noise and interference. Power-generating portions of the layout are the main cause of noise and so high switching current loop areas should be kept ...

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A5970AD compensate for the losses in the overall application. For this reason, the switching losses related to the R DSON ● Switching losses due to turning ON and OFF. These are derived using the following equation: Equation ...

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Application information R has a typical value of 0. °C and increases maximum value of 0.5. @ DS(on) 150 °C. We can consider a value of 0.4 Ω approximately 70 ns ...

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A5970AD In short-circuit conditions V is very small as equal to the voltage drop across parasitic components (typically the DCR of the inductor and the V the inductor is instead maximized as approximately equal the Equation 28 ...

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Application information Figure 16. Short-circuit current V Figure 17. Short-circuit current V 8.5 Application circuit Figure 18 shows the evaluation board application circuit, where the input supply voltage can range from and the ...

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... V C1206C221J5GAC 220 pF, 5 C1206C223K5RAC 22 nF, 10 5.6 kΩ, 1%, 0.1 W 0603 3.3 kΩ, 1%, 0.1 W 0603 4.7 kΩ, 1%, 0.1 W 0603 STPS3L40U DO3316T-153MLD 15 µH, 3.1 A Doc ID 14661 Rev 4 Application information Description Manufacturer 4.7 µ Murata Sanyo KEMET KEMET Neohm Neohm Neohm STMicroelectronics Coilcraft 29/42 ...

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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/ Doc ID 14661 Rev 4 A5970AD ...

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A5970AD 8.6 Positive buck-boost regulator The device can be used to implement a step-up/down converter with a positive output voltage. The output voltage is given by: Equation 32 where the ideal duty cycle D for the buck boost converter is: ...

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Application information Figure 22. Positive buck-boost regulator 8.7 Negative buck-boost regulator In Figure 23, the schematic circuit for a standard buck-boost topology is shown. The output voltage is: Equation 37 where the ideal duty cycle D for the buck boost ...

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A5970AD Figure 23. Negative buck-boost regulator 8.8 Synchronization example See Chapter 5.3 Figure 24. Synchronization example 8.9 Compensation network with MLCC at the output MLCCs (multiple layer ceramic capacitor) with values in the range of 10 µF-22 µF and rated ...

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Application information Equation 41 The figure below shows an example of a compensation network stabilizing the system with ceramic capacitors at the output (the optimum component value depends on the application). Figure 25. MLCC compensation network example 34/42 1 < ...

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A5970AD 8.10 External SOFT_START network At start-up the device can quickly increase the current up to the current limit in order to charge the output capacitor. If soft ramp-up of the output voltage is required, an external soft-start network can ...

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Typical characteristics 9 Typical characteristics Figure 27. Load regulation Vo (V) 3.312 Vcc = 12V 3.308 Vo = 3.3V 3.304 3.3 3.296 3.292 3.288 3.284 3.28 3.276 0 0.5 Figure 29. Output voltage vs junction temperature Vo (V) 1.25 1.24 ...

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A5970AD Figure 31. Junction temperature vs output current Figure 33. Efficiency vs output current Figure 32. Junction temperature vs output current Figure 34. Efficiency vs output current Doc ID 14661 Rev 4 Typical characteristics 37/42 ...

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Package mechanical data 10 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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A5970AD Table 10. SO-8 mechanical data Dim ( ddd 1. Dimensions D does not include mold flash, protrusions or gate burrs. Mold flash, potrusions or gate burrs shall ...

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Ordering information 11 Ordering information Table 11. Ordering information Order code A5970AD A5970ADTR 40/42 Package SO8 Doc ID 14661 Rev 4 A5970AD Packaging Tube Tape and reel ...

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A5970AD 12 Revision history Table 12. Document revision history Date 02-May-2008 27-Aug-2008 23-Apr-2009 06-Nov-2009 Revision 1 Initial release 2 Updated: coverpage and Table 4 on page 5 3 Updated first feature in coverpage Updated coverpage, 4 Figure 28, Figure 29 ...

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