a5975d STMicroelectronics, a5975d Datasheet
a5975d
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a5975d Summary of contents
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... step-down switching regulator for automotive applications HSOP8 - exposed pad Description The A5975D is a step-down monolithic power switching regulator with a minimum switch current limit of 3. therefore able to deliver current to the load depending on the application conditions. The output voltage can be set from 1 ...
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... PWM comparator and power stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.7 Inhibit function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.8 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6 Additional features and protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1 Feedback disconnection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.2 Output overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.3 Zero load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7 Closing the loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 7.1 Error amplifier and compensation network . . . . . . . . . . . . . . . . . . . . . . . . 19 7.2 LC filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.3 PWM comparator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 8 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2/50 Doc ID 018760 Rev 1 A5975D ...
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... A5975D 8.1 Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8.2 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.3 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.3.1 8.3.2 8.4 RMS current of the embedded power MOSFET . . . . . . . . . . . . . . . . . . . 32 8.5 Short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 8.6 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 8.7 Positive buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 8.8 Negative buck-boost regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 8.9 Floating boost current generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 8.10 Synchronization example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 8.11 Compensation network with MLCC at the output . . . . . . . . . . . . . . . . . . . 41 8.12 External soft-start network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 9 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 10 Package mechanical data ...
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... Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Table 2. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Table 3. Thermal data Table 4. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 5. Uncompensated error amplifier characteristics Table 6. List of ceramic capacitors for the A5975D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Table 7. Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Table 8. Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Table 9. Component list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Table 10. HSOP8 mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Table 11. Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Table 12 ...
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... A5975D List of figures Figure 1. Application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 2. Pin connection (top view Figure 3. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figure 4. Internal circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 5. Oscillator circuit block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Figure 6. Synchronization example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 7. Current limitation circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Figure 8. Driving circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 9. Block diagram of the loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 10. Error amplifier equivalent circuit and compensation network . . . . . . . . . . . . . . . . . . . . . . . 20 Figure 11 ...
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... When it is open an internal pull-up disables the device. E/A output for frequency compensation. Feedback input. Connecting directly to this pin results in an output voltage of 1. external resistive divider is required for higher output voltages. 3 cap is requested for stability. REF REF Ground. Unregulated DC input voltage. CC Doc ID 018760 Rev 1 Description A5975D ...
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... A5975D 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 Analog pins INH 3 V SYNCH 2 P Power dissipation at T TOT T Operating junction temperature range ...
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... V = 1.9 V COMP Doc ID 018760 Rev 1 Min. Typ. Max 0.250 3.75 4.5 5.25 212 250 0 1.198 1.235 1.272 2.2 3 190 300 1 2.3 A5975D Unit 36 V Ω 0.5 A 280 kHz 100 % 2.5 mA μA 100 μA 100 0 0.4 V μA mA μ ...
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... A5975D 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 ...
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... T temperature. All the datasheet parameters can be guaranteed to a maximum junction temperature of +125 °C, to avoid triggering the thermal shutdown protection during the testing phase due to self heating. 10/50 Section 2.2). SHTDWN Doc ID 018760 Rev 1 A5975D (+150 °C ±10 °C) ...
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... A5975D 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 which checks the input and the internal voltages A fully integrated sawtooth oscillator with a frequency of 250 kHz ± 15%, including also ● ...
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... Beating frequency noise is an issue when more than one voltage rail is on the same board. A simple way to avoid this issue is to operate all the regulators at the same switching frequency. The synchronization feature set of the A5975D, is simply obtained by connecting together their SYNCH pins. The device with highest switching frequency is the master, 12/50 ...
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... A5975D 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 the master device is recommended for its proper REF operation. However, when a set of synchronized devices populate a board it is not possible to know in advance which is working as master, so the filtering capacitor must be designed for a whole set of devices ...
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... Figure 6. Synchronization example 5.4 Current protection The A5975D 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 power PDMOS transistor is split into two parallel PDMOS transistors. ...
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... A5975D 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 the inverting input (FB) is connected to the external divider or directly to the output voltage. The output (COMP) is connected to the external compensation network ...
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... V against any cross conduction between the supply line and ground. Figure 8. Driving circuitry 16/50 Figure 8). The basic idea is to change the current levels used to turn GSmax Doc ID 018760 Rev 1 . The on/off control block protects A5975D GS ...
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... A5975D 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 the INH pin lower than 0.8 V, the device is enabled. If the INH pin is left floating, an internal pull-up ensures that the voltage at the pin reaches the inhibit threshold and the device is disabled ...
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... Due to the fact that the internal power is a PDMOS, no bootstrap capacitor is required and so the device works properly even with no load at the output. In this case it works in burst mode, with a random burst repetition rate. 18/ ⋅ ⋅ ------------------- - 1.3 OVP Doc ID 018760 Rev 1 A5975D (Figure 19), the OVP 2 ...
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... A5975D 7 Closing the loop Figure 9. Block diagram of 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. The simplest compensation network, together with the equivalent circuit of the error amplifier, are shown in loop gain ...
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... LC filter (see below). F frequency. 20/50 >> --------------------------------- - P1 2 π R ⋅ ⋅ ⋅ --------------------------------------------------- - P2 2 π R ⋅ ⋅ ⋅ --------------------------------- Z1 2 π R ⋅ ⋅ ⋅ Doc ID 018760 Rev 1 A5975D is usually put near usually at a very high P2 ...
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... A5975D 7.2 LC filter The transfer function of the LC filter is given by: Equation where R is defined as the ratio between V LOAD If R >>ESR, the previous expression of A LOAD Equation 7 The zero of this transfer function is given by: Equation the zero introduced by the ESR of the output capacitor and it is very important to 0 increase the phase margin of the loop ...
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... 220 µF and ESR = 25 mΩ, the poles and zeroes of A OUT = 3.3 kΩ. 2 Doc ID 018760 Rev – V OSCMIN is the OSCMIN ⋅ const ⋅ ⋅ 120 pF, the poles and zeroes Figure 11 and 12. A5975D . CC are: 0 become: ...
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... A5975D Figure 11. Module plot Figure 12. Phase plot The cut-off frequency and the phase margin are: Equation 38kHz Phase margin = 45° C Doc ID 018760 Rev 1 Closing the loop 23/50 ...
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... RMS O 2 η OUT ------------------------------------ - MAX V V – INMIN OUT ------------------------------------- - MIN V V – INMAX possible to determine the max. MIN MAX Doc ID 018760 Rev 1 A5975D is the output DC O the voltage drop across the ...
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... However, they can occasionally burn if subjected to very high current during charge. Therefore better to avoid this type of capacitor for the input filter of the device. They can, however, be subjected to high surge current when connected to the power supply. Table 6. List of ceramic capacitors for the A5975D Manufacturer TAIYO YUDEN MURATA ● ...
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... ---- - Series Inductor value (µH) DO3316T MSS1260T WE-PD L Figure 13 below. Doc ID 018760 Rev 1 Table 8, some inductor Saturation current (A) 5 3.5 to 4 A5975D ...
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... A5975D 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 to the ambient. For this device, the path through the exposed pad is the one conducting the largest amount of heat ...
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... OFF ⋅ ⋅ ⋅ ----------------------------------- - OUT SW 2 represent the switching times of the power element that cause the FALL ⋅ Doc ID 018760 Rev 1 ⋅ ⋅ ⋅ OUT SW SW Figure 14 the equivalent A5975D ...
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... A5975D The overall losses are: Equation The junction temperature of device is: Equation 27 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 static thermal performance and not by the electrical performance of the device ...
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... V =12 V and main output rails the device can deliver 3 A continuously (see OUT Δ Doc ID 018760 Rev 1 = 250 kHz) SW =3.3 V, where the OUT = 250 kHz) SW Figure Δ switching loss + quiescent loss) < A5975D 17) because Δ ...
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... The characterization of the thermal impedance is strictly dependent on the layout of the board. In Figure 17 of the A5975D is provided. 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 short pulses, the device can deliver a higher output current value. Δ ...
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... Application information 8.4 RMS current of the embedded power MOSFET As the A5975D embeds the high side switch, the internal power dissipation is sometimes the bottleneck for the output current capability (refer to operating temperature). Nevertheless, as mentioned in the general description continuous output current most of the application conditions. ...
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... A5975D This can be understood considering the inductor current ripple during the ON and OFF phases: ● ON phase Equation 29 ● OFF phase Equation 30 where V is the voltage drop across the diode, DCR D In short-circuit conditions very small, as equal to the voltage drop across parasitic components (typically the DCR of ...
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... Application information Figure 19. Short-circuit current V Figure 20. Short-circuit current V 34/ Doc ID 018760 Rev 1 A5975D ...
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... A5975D Figure 21. Short-circuit current V 8.6 Application circuit Figure 22 shows the demonstration board application circuit, where the input supply voltage can range from and the output voltage is adjustable from 1.235 due to the voltage rating of the output capacitor. Figure 22. Demonstration board application circuit ...
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... POSCAP 6TVB330ML 330 µH, 25 mΩ 5.6 kΩ, 1%, 0.1 W 0603 3.3 kΩ, 1%, 0.1 W 0603 10 kΩ, 1%, 0.1 W 0603 STPS5L60S MSS1246T-123 12 µH, I Doc ID 018760 Rev 1 Description Manufacturer Taiyo Yuden Sanyo STMicroelectronics 3A Coilcraft RMS 20°C A5975D ...
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... A5975D Figure 25. PCB layout (front side) 8.7 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: Equation 34 However, due to power losses in the passive elements, the real duty cycle is always higher than this ...
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... Also can be used to calculate the maximum output current. So, for example OUT Doc ID 018760 Rev 1 ⋅ – D ⋅ ------------ - 1 D – OUT = 0.5 A: LOAD A5975D 6 470 Ω ESR>35m AM09693v1 ...
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... Floating boost current generator The A5975D 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 load can be floating. A typical example is a current generator for LED driving, as the LED does not require a connection to the ground ...
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... OFF phase. 40/ ------------ - OUT 1 D – V – V OUT ----------------------------- - V OUT Section 8 LOAD RIPPLE LOAD I = -------------- - + ------------------- - = -------------- - – – I LOAD I = -------------- - – Doc ID 018760 Rev 1 A5975D and Section 8.8.) the measured ⋅ ---------- - --------- + ⋅ ...
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... Figure 30. Synchronization example 8.11 Compensation network with MLCC at the output The A5975D standard compensation network (please refer to introduces a single zero and a low frequency pole in the system bandwidth high ESR output capacitor must be selected to compensate the 180-degree phase shift given by the LC double pole. ...
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... This configuration introduces two zeros and a low frequency pole in the designed bandwidth and so guarantees a proper phase margin. Figure 31. MLCC compensation network circuit 42/50 1 < ----------------------------------------------- - bandwidth 2 π ESR C ⋅ ⋅ ⋅ Z ESR OUT < < ⋅ ESR Doc ID 018760 Rev 1 A5975D ...
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... A5975D 8.12 External soft-start network At startup, 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 be implemented, as shown external reference through R and the BJT clamps the COMP pin. ...
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... Typical characteristics 9 Typical characteristics Figure 33. Line regulator Figure 35. Output voltage vs. junction temperature Figure 37. Quiescent current vs. junction temperature 44/50 Figure 34. Shutdown current vs. junction temperature Figure 36. Switching frequency vs. junction temperature Figure 38. Junction temperature vs. output current (V Doc ID 018760 Rev 1 A5975D ...
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... A5975D Figure 39. Junction temperature vs. output current (V Figure 41. Efficiency vs. output current (V IN Figure 40. Efficiency vs. output current Doc ID 018760 Rev 1 Typical characteristics ( 45/50 ...
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... Typ. Max. 1.70 0.00 0.10 1.25 0.31 0.51 0.17 0.25 4.80 4.90 5.00 3 3.1 3.2 5.80 6.00 6.20 3.80 3.90 4.00 2.31 2.41 2.51 1.27 0.25 0.50 0.40 1.27 0° (min), 8° (max) 0.10 Doc ID 018760 Rev 1 A5975D inch Min. Typ. Max. 0.0669 0.00 0.0039 0.0492 0.0122 0.0201 0.0067 0.0098 0.1890 0.1929 0.1969 0.118 0.122 0.126 0.2283 0.2441 0.1496 0.1575 0.091 0.095 0.099 0.0098 0.0197 0.0157 0.0500 0.0039 ...
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... A5975D Figure 42. Package dimensions Doc ID 018760 Rev 1 Package mechanical data 47/50 ...
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... Ordering information 11 Ordering information Table 11. Ordering information Order codes A5975D A5975DTR 48/50 Package HSOP8 Doc ID 018760 Rev 1 A5975D Packaging Tube Tape and reel ...
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... A5975D 12 Revision history Table 12. Document revision history Date 19-Apr-2011 Revision 1 Initial release Doc ID 018760 Rev 1 Revision history Changes 49/50 ...
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... Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 50/50 Please Read Carefully: © 2011 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com Doc ID 018760 Rev 1 A5975D ...