SLVSDJ1A July 2016 – May 2017 TPS65381A-Q1
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The TPS65381A-Q1 device is a multirail power supply including one buck preregulator, one linear controller, one 5-V linear regulator, one programmable 3.3-V or 5-V linear regulator, and one linear tracking regulator with protection against short to battery and ground. The device has many diagnostic and monitoring functions. This device provides a power-management basis for many different applications.
The following design requirements and design procedure are an example of how to select component values for the TPS65381A-Q1 device for a typical application. Because many of the regulators are adjustable, the equations should be used to calculate the component values for the specific application. For additional reference, also refer to the design checklist and application notes listed in Section 9.1.1.
NOTE:
While selecting capacitors for the application consider the following characteristics:
These impacts must all be considered when selecting a capacitor so that the circuit has the specified capacitance required for this device at the application operating conditions of the capacitor such as temperature, voltage, and lifetime.
The VBATP and VBAT_SAFING pins are the supply inputs to the device. These supplies must be reverse-battery protected. The supplies should also be adequately protected against transients and have sufficient noise filtering for the intended application. If the application has noisy and high-current output drives that are connected to either the VBATP pin, VBAT_SAFING pin, or both, additional filtering may be necessary between the output drive and the device.
The IGN pin is a wake-up input to the device. This input provides up to –7 V of protection. Beyond this voltage, the IGN pin must be reverse protected. If the noise can occur longer than the specified deglitch time, the IGN pin should also be adequately protected against transients and have sufficient noise filtering for the intended application.
The inductor, output capacitor, and total effective series resistance (ESR) of the output capacitance must be considered to achieve balanced operation of the VDD6 preregulator.
The output inductor must be greater than or equal to the minimum 22-μH inductance. The typical specified inductance is 33 μH, which was selected for this design.
The effective output capacitance for the VDD6 preregulator is specified from 22 μF to 47 μF. An effective capacitance of 22 μF at the 6-V DC operating point was selected for this design. This value allows for additional downstream input capacitance on voltage regulator inputs. To filter high frequencies, use 10-nF and 0.1-μF capacitors in parallel. If higher effective capacitance is used, the voltage ripple is reduced and lowers the required ESR. The effective capacitance of a capacitor should be provided by the capacitor supplier and must be derated for tolerance, lifetime, temperature, and operating voltage.
Because the VDD6 preregulator is a hysteretic architecture, controlled ESR is required with the output capacitance. The specified ESR range is from 100 mΩ to 300 mΩ. Use Equation 1 to calculate the minimum total ESR to achieve balanced operation.
As an example, the data sheet for the capacitor states that the ESR of the capacitor is 4 mΩ and the parasitic extraction of the PCB design is 6 mΩ. An ESR resistor of 100 mΩ can still be used, or the discrete ESR resistor can be sized to 90 mΩ resulting in a total effective ESR of at least 100 mΩ. If a larger effective capacitance is used, the equation may result in an ESR value below 100 mΩ. In this case, the total ESR should still be brought up to 100-mΩ total ESR minimum to meet the specification.
A high-voltage surface-mount Schottky-rectifier diode, such as SS3H9/10 or MBRS340T3, should be used.
Figure 6-2 shows this configuration.
The microprocessor used with the TPS65381A-Q1 device requires a core voltage of 1.23 V.
The output voltage of the VDD1 linear controller is set by a resistor divider from the VDD1 output to ground with the divided voltage connected to the VDD1_SENSE pin, which must be set to 800 mV. To ensure sufficient bias current through the resistor divider, select a value of R1 as 80.6 Ω. Use Equation 2 to calculate the resistance of R2.
Select the standard value of 43.2 Ω.
NOTE
The tolerance of the R1 and R2 resistors in this resistor divider will impact the VDD1 regulation and voltage monitoring tolerance. Resistors with 0.1% tolerance are recommended.
Select an output FET for the VDD1 linear controller that meets the requirements in the VDD1 – LDO With External FET specifications in Section 4.5. An example output FET is BUK9213-30A. The gate of the output FET is connected to the VDD1_G pin. A 100-kΩ resistor is connected between the gate and source of the FET. The drain of the FET is connected to the VDD6 preregulator output, which is used as the supply input for the VDD1 linear controller.
A low-ESR ceramic output capacitor with 22-μF effective capacitance at 1.23 V is used to meet the requirements for the output capacitor that is listed in this data sheet. Depending on the application, this output may require a larger output capacitor to ensure the output does not drop below the required regulation specification during load transients. The VDD1 output capacitance is specified up to 40 μF.
Figure 6-3 shows this configuration.
The system has a sensor that requires a 5-V supply that must track the VDD5 supply. The configuration should be set up for higher efficiency.
The VDD5 output is connected to the VTRACK1 pin, which configures the regulator for tracking mode. Because the output must track the input, unity gain feedback is used on the VSFB1 pin by connecting it to the VSOUT1 pin.
For efficiency, use the VDD6 preregulator as the supply. Therefore, the VDD6 output is connected to VSIN. A local, low-ESR 100-nF ceramic capacitor is used on the VSIN pin to stabilize the input.
A local, low-ESR 4.7-μF ceramic capacitor is used on the VSOUT1 output for loop stabilization. Depending on the application, this output may require a larger output capacitor to ensure that the output does not drop below the required regulation specification during load transients. The VSOUT1 output capacitance is specified up to 10 μF.
Figure 6-4 shows this configuration.
The system has a sensor that requires a 6-V supply that must track the VDD3/5 supply operating at 3.3 V.
The VDD3/5 supply, operating in 3.3-V mode, is connected to the VTRACK1 pin, which configures the regulator for tracking mode. Because the output must have gain to make the 6-V output track a 3.3-V supply, gain feedback is used on the VSFB1 pin. To achieve the required gain, connect a resistor divider the VSOUT1 and VSFB1 pins. Select a value of 3.3 kΩ for the RVSFB1 resistor to balance the current through the resistor divider for reasonable bias current and reasonable losses. Use Equation 3 to calculate the resistance of RVSFB2.
Select the standard value of 2.7 kΩ.
NOTE
The tolerance of the RVSFB1 and RVSFB2 resistors in this resistor divider will impact the VSOUT1 regulation and voltage monitoring tolerance. Resistors with 0.1% tolerance are recommended.
Because the desired VSOUT1 output is greater than 5 V, the VBATP supply must be used for the tracking supply. Therefore, connect the VBATP supply to the VSIN pin. A local, low-ESR 100-nF ceramic capacitor is used on the VSIN pin to stabilize the input.
A local, low-ESR 4.7-μF ceramic capacitor is used on the VSOUT1 pin for loop stabilization. Depending on the application, this output may require a larger output capacitor to ensure that the output does not drop below the required regulation specification during load transients. The VSOUT1 output capacitance is specified up to 10 μF.
Figure 6-5 shows this configuration.
The system has a sensor that requires a 9-V supply that must track the VDD5 supply operating at 5 V.
The VDD5 supply is connected to VTRACK1, which configures the regulator for tracking mode. Because the output must have gain to make the 9-V output track a 5-V supply, gain feedback is used on the VSFB1 pin. To achieve the required gain, connect a resistor divider between the VSOUT1 and VSFB1 pins. Select a value of 3.3 kΩ for the RVSFB1 resistor to balance the current through the resistor divider for reasonable bias current and reasonable losses. Use Equation 4 to calculate the resistance of RVSFB2.
Select the standard value of 2.7 kΩ.
NOTE
The tolerance of the RVSFB1 and RVSFB2 resistors in this resistor divider will impact the VSOUT1 regulation and voltage monitoring tolerance. Resistors with 0.1% tolerance are recommended.
Because the desired VSOUT1 output is greater than 5-V, the VBATP supply must be used as the tracking supply. Therefore, connect the VBATP supply to the VSIN pin. A local, low-ESR 100-nF ceramic capacitor is used on the VSIN pin to stabilize the input.
A local, low-ESR 4.7-μF ceramic capacitor is used on the VSOUT1 pin for loop stabilization. Depending on the application, this output may require a larger output capacitor to ensure that the output does not drop below the required regulation specification during load transients. The VSOUT1 output capacitance is specified up to 10 μF.
Figure 6-6 shows this configuration.
If the system requires a 4.5-V supply that does not track any other supply, the VTRACK1 pin is connected to ground (GND), which configures the regulator for non-tracking mode. The output is now proportional to a fixed reference voltage (Vref) of 2.5 V on the VSFB1 pin. Because the output must have gain to result in a 4.5-V output, gain feedback will be used on the VSFB1 pin. To achieve the required gain, connect a resistor divider between the VSOUT1 and VSFB1 pins. Select a value of 3.3 kΩ for the RVSFB1 resistor to balance the current through the resistor divider for reasonable bias current and reasonable losses. Use Equation 5 to calculate the resistance of RVSFB2.
Select the standard value of 2.7 kΩ.
NOTE
The tolerance of the RVSFB1 and RVSFB2 resistors in this resistor divider will impact the VSOUT1 regulation and voltage monitoring tolerance. Resistors with 0.1% tolerance are recommended.
For efficiency, the VDD6 preregulator is the supply and therefore the VDD6 output is connected to the VSIN pin. A local, low-ESR 100-nF ceramic capacitor is used on the VSIN pin to stabilize the input.
A local, low-ESR 4.7-μF ceramic capacitor is used on the VSOUT1 pin for loop stabilization. Depending on the application, this output may require a larger output capacitor to ensure that the output does not drop below the required regulation specification during load transients. The VSOUT1 output capacitance is specified up to 10 μF.
Figure 6-7 shows this configuration.
For the application curves, see the figures listed in Table 6-1.
FIGURE TITLE | FIGURE NUMBER |
---|---|
SPI SDO Buffer Source and Sink Current | Figure 4-3 |
VDD6 BUCK Efficiency | Figure 4-4 |