JAJSD93 June 2017 TPS82150
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 output voltage of the TPS82150 is adjusted by component selection. The following section discusses the design of the external components to complete the power supply design for several input and output voltage options by using typical applications as a reference.
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For this design example, use the following as the input parameters.
DESIGN PARAMETER | EXAMPLE VALUE |
---|---|
Input voltage range | 12V |
Output voltage | 1.8V |
Output ripple voltage | < 20mV |
Output current rating | 1A |
The components used for measurements are given in the following table.
REFERENCE | DESCRIPTION(1) | MANUFACTURER |
---|---|---|
C1 | 10 µF, 25 V, X7R, ±20%, size 1206, C3216X7R1E106M160AE | TDK |
C2 | 22 µF, 10 V, X7S, ±20%, size 0805, C2012X7S1A226M125AC | TDK |
C3 | 3300 pF, 50 V, ±5%, C0G/NP0, size 0603, GRM1885C1H332JA01D | Murata |
R1, R2, R3 | Standard |
Click here to create a custom design using the TPS82150 device with the WEBENCH® Power Designer.
The output voltage is set by an external resistor divider according to the following equations:
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R2 should not be higher than 100kΩ to achieve high efficiency at light load while providing acceptable noise sensitivity. Larger currents through R2 improve noise sensitivity and output voltage accuracy. Figure 5 shows the external resistor divider value for a 1.8-V output. Choose appropriate resistor values for other outputs.
In case the FB pin gets opened, the device clamps the output voltage at the VOUT pin internally to about 7V.
For best output and input voltage filtering, low ESR ceramic capacitors are required. The input capacitor minimizes input voltage ripple, suppresses input voltage spikes and provides a stable system rail for the device. A 10-µF or larger input capacitor is required. The output capacitor value can range from 22μF up to more than 400μF. Higher values are possible as well and can be evaluated through the transient response. Larger soft start times are recommended for higher output capacitances.
High capacitance ceramic capacitors have a DC Bias effect, which will have a strong influence on the final effective capacitance. Therefore the right capacitor value has to be chosen carefully. Package size and voltage rating in combination with dielectric material are responsible for differences between the rated capacitor value and the effective capacitance.
A capacitance connected between the SS/TR pin and the GND allows programming the startup slope of the output voltage. A constant current of 2.5 μA charges the external capacitor. The capacitance required for a given soft startup time for the output voltage is given by:
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TA = 25°C, VIN = 12 V, VOUT = 1.8 V, unless otherwise noted.
θJA = 46.1 °C/W |
θJA = 46.1 °C/W |
VOUT = 1.8V |
IOUT = 1A |
IOUT = 0A to 1A, 1A/µs |
No Load |
θJA = 46.1 °C/W |
θJA = 46.1 °C/W |
IOUT = 1A |
IOUT = 1A |
No Load |
IOUT = 0.5A to 1A, 1A/µs |
ROUT = 1.8Ω |
The TPS82150 can be used as inverting power supply by rearranging external circuitry as shown in Figure 30. As the former GND node now represents a voltage level below system ground, the voltage difference between VIN and VOUT has to be limited for operation to the maximum supply voltage of 17V (see Equation 8).
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The transfer function of the inverting power supply configuration differs from the buck mode transfer function, incorporating a Right Half Plane Zero additionally. Therefore the loop stability has to be adapted. More detailed information is given in TIDUCV2.