A5974ADTR STMicroelectronics, A5974ADTR Datasheet
A5974ADTR
Specifications of A5974ADTR
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A5974ADTR Summary of contents
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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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A5974AD 8.1 Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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List of tables List of tables Table 1. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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A5974AD List of figures Figure 1. Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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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 GND 8 V 6/49 ...
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A5974AD 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 ° Table 4. Electrical characteristics Symbol Operating input V CC voltage range MOSFET on- R DS(on) resistance Maximum limiting I L current f Switching frequency SW Duty ...
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A5974AD 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. Guaranteed by design. Parameter Test condition V ...
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Datasheet parameters over the temperature range 4 Datasheet parameters over the temperature range 100% of the population in the production flow is tested at three different ambient temperatures (-40 °C, +25 °C, and +125 °C) to guarantee the datasheet parameters ...
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A5974AD 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 5.1 Power supply and voltage reference The internal regulator circuit (shown in voltage pre-regulator, the bandgap voltage reference and the bias block that provides current to all the blocks. The starter supplies the start-up currents to the entire ...
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A5974AD which provides the synchronization signal to the others. Therefore the SYNCH is an I/O pin to deliver or recognize a frequency signal. The synchronization circuitry is powered by the internal reference (V V pin and the signal ground of ...
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Functional description Figure 6. Synchronization example 5.4 Current protection The A5974AD features two types of current limit protection; pulse-by-pulse and frequency foldback. The schematic of the current limitation circuitry for the pulse-by-pulse protection is shown in Figure 7. The output ...
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A5974AD Figure 7. Current limitation circuitry 5.5 Error amplifier The voltage error amplifier is the core of the loop regulation transconductance operational amplifier whose non inverting input is connected to the internal voltage reference (1.235 V), while ...
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Functional description However, there is a limit introduced by the recovery time of the recirculation diode. In fact, when the current of the power element is equal to the inductor current, the diode turns off and the drain of the ...
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A5974AD 5.7 Inhibit function The inhibit feature is used to put the device in standby mode. With the INH pin higher than 2.2 V, the device is disabled and the power consumption is reduced to less than 100 µA. With ...
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Additional features and protection 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 ...
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A5974AD 7 Closing the loop Figure 9. Block diagram of the loop Doc ID 018762 Rev 1 Closing the loop 19/49 ...
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Closing the loop 7.1 Error amplifier and compensation network The output LC filter of a step-down converter contributes with 180-degree phase shift in the control loop. For this reason a compensation network between the COMP pin and GROUND is added. ...
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A5974AD 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 LC filter (see below). F frequency. 7.2 LC filter ...
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Closing the loop 7.3 PWM comparator The PWM gain is given by the following formula: Equation 12 where V is the maximum value of a sawtooth waveform and V OSCMAX minimum value. A voltage feed-forward is implemented to ensure a ...
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A5974AD Figure 11. Module plot Figure 12. Phase plot The cut-off frequency and the phase margin are: Equation 38kHz Phase margin = 52° C Doc ID 018762 Rev 1 Closing the loop 23/49 ...
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Application information 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. As step-down converters draw current from the input in pulses, ...
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A5974AD ● Tantalum capacitors: Very good, small tantalum capacitors with very low ESR are becoming more available. However, they can occasionally burn if subjected to very high current during charge Therefore better to avoid this type of capacitor ...
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Application information where T is the ON time of the internal switch, given by D · T. For example, with 3 OUT IN current through the inductor is given by: Equation 21 and it can ...
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A5974AD Figure 13. Layout example 8.3 Thermal considerations 8.3.1 Thermal resistance the equivalent static thermal resistance junction-to-ambient of the device; it can be THJ-A calculated as the parallel of many paths of heat conduction from the junction ...
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Application information where T and T RISE switching losses when driving an inductive load (see switching time. Figure 14. Switching losses ● Quiescent current losses. Equation 25 where I is the quiescent current. Q Example: – ...
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A5974AD Equation 28 8.3.2 Thermal impedance Z The thermal impedance of the system, considered as the device in the HSO8 package soldered on the application board, takes on an important rule when the maximum output power is limited by the ...
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Application information continuous output current the load, however, the maximum power loss of 1 reached with an output current of 1 the maximum output power is derated if =80 °C. T ...
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A5974AD Figure 17. Measurement of the thermal impedance of the demonstration board As can be seen, for example, for load pulses with a duration of 1 second, the actual thermal impedance is lower than 20 °C/W. This means that, for ...
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Application information the inductor and the V to the inductor is instead maximized as approximately equal to V So, Equation 29 and the Equation 31 considering T , which has already been reduced to its minimum. ON Equation 32 Δ ...
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A5974AD Figure 19. Short-circuit current V Figure 20. Short-circuit current Doc ID 018762 Rev 1 Application information 33/49 ...
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... V 68 nF, 5%, 0603 150 pF, 5%, 0603 22 nF, 5%, 0603 POSCAP 6TVB330ML 330 µF, 25 mΩ 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 MSS1246T-123ML 12 µH, I Doc ID 018762 Rev 1 A5974AD Manufacturer Taiyo Yuden Sanyo STMicroelectronics 20° Coilcraft RMS ...
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A5974AD Figure 22. PCB layout (component side) Figure 23. PCB layout (bottom side) Figure 24. PCB layout (front side) Doc ID 018762 Rev 1 Application information 35/49 ...
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Application information 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 33 where the ideal duty cycle D for the buck-boost converter is: ...
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A5974AD Figure 25. Positive buck-boost regulator 10V 4.7 6.8 8.7 Negative buck-boost regulator In Figure 26, the schematic circuit for a standard buck-boost topology is shown. The output voltage is: Equation 38 where the ideal duty cycle D for the ...
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Application information Figure 26. Negative buck-boost regulator 8.8 Floating boost current generator The A5974AD does not support a nominal boost conversion as this topology requires a low side switch, however, a floating boost can be useful in applications where the ...
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A5974AD Figure 28. 350 mA LED boost current source The device is powered from the output voltage so the maximum voltage drop across the LEDs and resistor sense The output voltage is given by: Equation 42 where ...
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Application information As a consequence, the maximum output current is: Equation 46 where I represents the rated current of the device. SW MAX Figure 28 shows a tested circuit to implement a boost current source for high current LED driving ...
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A5974AD MLCCs (multiple layer ceramic capacitor) with values in the range of 10 µF-22 µF and rated voltages in the range of 10 V-25 V are available today at relatively low cost from many manufacturers. These capacitors have very low ...
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Application information Figure 31. Soft-start network example 42/49 Doc ID 018762 Rev 1 A5974AD ...
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A5974AD 9 Typical characteristics Figure 32. Line regulator Figure 34. Output voltage vs. junction temperature Figure 36. Junction temperature vs. output current (V Figure 33. Shutdown current vs. junction temperature Figure 35. Junction temperature vs. output current (V Figure 37. ...
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Typical characteristics Figure 38. Efficiency vs. output current (V 44/ Doc ID 018762 Rev 1 A5974AD ...
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A5974AD 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 at: www.st.com. ...
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Package mechanical data Table 10. HSOP8 mechanical data Dim. Min ccc Figure 39. Package dimensions 46/49 mm Typ. Max. 1.70 0.00 0.10 1.25 0.31 0.51 0.17 ...
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... A5974AD 11 Ordering information Table 11. Ordering information Order codes A5974AD A5974ADTR Package HSOP8 Doc ID 018762 Rev 1 Ordering information Packaging Tube Tape and reel 47/49 ...
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Revision history 12 Revision history Table 12. Document revision history Date 19-Apr-2011 48/49 Revision 1 Initial release Doc ID 018762 Rev 1 A5974AD Changes ...
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... A5974AD 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. ...