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SLVS576B SEPTEMBER 2005 – January 2016 TPS65150

PRODUCTION DATA.

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)

RGE|24
PWP|24

散热焊盘机械数据 (封装 | 引脚)

订购信息

8 Application and Implementation

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.

8.1 Application Information

The TPS65150 device has been designed to provide the input supply voltages for the source drivers and gate drivers plus the voltage for the common plane in LCD display applications. In addition, the device provides a gate voltage shaping function that can be used to modulate the gate drivers' positive supply to reduce image sticking.

8.2 Typical Application

Figure 17 shows a typical application circuit for a monitor display powered from a 5-V supply. It generates up to 450 mA at 13.5 V to power the source drivers, and 20 mA at 23 V and –5 V to power the gate drivers.

Figure 17. Monitor LCD Supply Powered from a 5-V Rail

8.2.1 Design Requirements

Table 2 shows the design parameters for this example.

Table 2. Design Requirements

PARAMETER	SYMBOL	VALUE
Input supply voltage	V_I	5 V
Boost converter output voltage and current	V_(VS)	13.5 V at 450 mA
Boost converter peak-to-peak output voltage ripple	V_(VS)(PP)	10 mV
Positive charge pump output voltage and current	V_(CPI)	23 V at 20 mA
Positive charge pump peak-to-peak output voltage ripple	V_(VGH)(PP)	100 mV
Negative charge pump output voltage and current	V_(VGL)	–5 V at 20 mA
Negative charge pump peak-to-peak output voltage ripple	V_(VGL)(PP)	100 mV
Negative charge pump start-up delay time	t_d1	1 ms
Positive charge pump start-up delay time	t_d2	1 ms
Fault delay time	t_d(fault)	45 ms
Gate voltage shaping slope		10 V/µs

8.2.2 Detailed Design Procedure

8.2.2.1 Boost Converter Design Procedure

8.2.2.1.1 Inductor Selection

Several inductors work with the TPS65150, and with external compensation the performance can be adjusted to the specific application requirements.

The main parameter for the inductor selection is the inductor saturation current, which should be higher than the peak switch current as calculated in Equation 2 with additional margin to cover for heavy load transients. The alternative, more conservative approach, is to choose the inductor with a saturation current at least as high as the maximum switch current limit of 3.4 A.

The second important parameter is the inductor DC resistance. Usually, the lower the DC resistance the higher the efficiency. It is important to note that the inductor DC resistance is not the only parameter determining the efficiency. For a boost converter, where the inductor is the energy storage element, the type and material of the inductor influences the efficiency as well. Especially at a switching frequency of 1.2 MHz, inductor core losses, proximity effects, and skin effects become more important. Usually, an inductor with a larger form factor gives higher efficiency. The efficiency difference between different inductors can vary from 2% to 10%. For the TPS65150, inductor values from 3.3 µH and 6.8 µH are a good choice, but other values can be used as well. Possible inductors are shown in Table 3. Equivalent parts can also be used.

Table 3. Inductor Selection

INDUCTANCE	I_SAT	DCR	MANUFACTURER	PART NUMBER	DIMENSIONS
4.7 µH	2.6 A	54 mΩ	Coilcraft	DO1813P-472HC	8.89 mm × 6.1 mm × 5 mm
4.2 µH	2.2 A	23 mΩ	Sumida	CDRH5D28 4R2	5.7 mm × 5.7 mm × 3 mm
4.7 µH	1.6 A	48 mΩ	Sumida	CDC5D23 4R7	6 mm × 6 mm × 2.5 mm
4.2 µH	1.8 A	60 mΩ	Sumida	CDRH6D12 4R2	6.5 mm × 6.5 mm × 1.5 mm
3.9 µH	2.6A	20 mΩ	Sumida	CDRH6D28 3R9	7 mm × 7 mm × 3 mm
3.3 µH	1.9 A	50 mΩ	Sumida	CDRH6D12 4R2	6.5 mm × 6.5 mm × 1.5 mm

The first step in the design procedure is to verify whether the maximum possible output current of the boost converter supports the specific application requirements. A simple approach is to estimate the converter efficiency, by taking the efficiency numbers from the provided efficiency curves, or use a worst case assumption for the expected efficiency, for example, 75%.

From Figure 19, it can be seen that the boost converter efficiency is about 85% when operating under the target application conditions. Inserting these values into Equation 1 yields

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Equation 15. TPS65150 EQN_25_SLVS576.gif

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and from Equation 2, the peak switch current can be calculated as

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Equation 16. TPS65150 EQN_26_SLVS576.gif

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The peak switch current is the peak current that the integrated switch, inductor, and rectifier diode must be able to handle. The calculation must be done for the minimum input voltage where the peak switch current is highest. For the calculation of the maximum current delivered by the boost converter, it must be considered that the positive and negative charge pumps as well as the VCOM buffer run from the output of the boost converter as well.

8.2.2.2 Rectifier Diode Selection

The rectifier diode reverse voltage rating should be higher than the maximum output voltage of the converter (13.5 V in this application); its average forward current rating should be higher than the maximum boost converter output current of 450 mA, and its repetitive peak forward current should be greater than or equal to the peak switch current of 1.8 A. Not all diode manufacturers specify repetitive peak forward current; however, a diode with an average forward current rating of 1 A or higher is suitable for most practical applications.

From Equation 5, the power dissipated in the rectifier diode is given by

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Equation 17. TPS65150 EQN_29_SLVS576.gif

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Table 4 lists a number of suitable rectifier diodes, any of which would be suitable for this application. Equivalent parts can also be used.

Table 4. Rectifier Diode Selection

I_F(AV)	V_R	V_F	MANUFACTURER	PART NUMBER
2 A	20 V	0.44 V at 2 A	Vishay Semiconductor	SL22
2 A	20 V	0.5 V at 2 A	Fairchild Semiconductor	SS22
1 A	30 V	0.44 V at 2 A	Fairchild Semiconductor	MBRS130L
1 A	20 V	0.45 V at 1 A	Microsemi	UPS120
1 A	20 V	0.45 V at 1 A	ON Semiconductor	MBRM120

8.2.2.3 Setting the Output Voltage

Rearranging Equation 3 and inserting the application parameters, we get

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Equation 18. TPS65150 EQN_31_SLVS576.gif

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Standard values of R1 = 820 kΩ and R2 = 75 kΩ result in a nominal output voltage of 13.68 V and satisfy the recommendation that the value R1 be lower than 1 MΩ.

8.2.2.4 Output Capacitor Selection

For best output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low ESR value, but tantalum capacitors can be used as well, depending on the application. A 22-µF ceramic output capacitor works for most applications. Higher capacitor values can be used to improve the load transient regulation. See Table 5 for the selection of the output capacitor.

Rearranging Equation 6 and inserting the application parameters, the minimum value of output capacitance is given by Equation 19.

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Equation 19. TPS65150 EQN_28_SLVS576.gif

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The closest standard value is 22 µF. In practice, TI recommends connecting an additional 1-µF capacitor directly to the SUP pin to ensure a clean supply to the internal circuitry that runs from this supply voltage.

8.2.2.5 Input Capacitor Selection

For good input voltage filtering, low ESR ceramic capacitors are recommended. A 22-µF ceramic input capacitor is sufficient for most applications. For better input voltage filtering, this value can be increased. See Table 5 for input capacitor recommendations. Equivalent parts can also be used.

Table 5. Input and Output Capacitance Selection

CAPACITANCE	VOLTAGE RATING	MANUFACTURER	PART NUMBER	SIZE
22 µF	16 V	Taiyo Yuden	EMK325BY226MM	1206
22 µF	6.3 V	Taiyo Yuden	JMK316BJ226	1206

8.2.2.6 Compensation

From Table 1, it can be seen that the recommended values for C9 and R9 when V_I = 5 V are 2.2 nF and 0 Ω respectively, and that a feedforward zero at 11.2 kHz should be added.

Rearranging Equation 7, we get

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Equation 20. TPS65150 EQN_13_SLVS576.gif

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Inserting f_co = 11.2 kHz and R1 = 820 kΩ, we get

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In this case, a standard value of 22 pF was used.

8.2.2.7 Negative Charge Pump

8.2.2.7.1 Choosing the Output Capacitance

Rearranging Equation 9 and inserting the application parameters, the minimum recommended value of C3 is given by

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Equation 21. TPS65150 EQN_04_SLVS576.gif

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In this application, a capacitance of 330 nF was used to allow the same value to be used for all charge pump capacitances.

8.2.2.7.2 Choosing the Flying Capacitance

A minimum flying capacitance of 100 nF is recommended. In this application, a capacitance of 330 nF was used to allow the same value to be used for all charge pump capacitances.

8.2.2.7.3 Choosing the Feedback Resistors

From Equation 22, the ratio of R3 to R4 required to generate an output voltage of –5 V is given by

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Equation 22. TPS65150 EQN_05_SLVS576.gif

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Values of R3 = 620 kΩ and R4 = 150 kΩ generate a nominal output voltage of –5.014 V and load the REF pin with only 8 µA.

8.2.2.7.4 Choosing the Diodes

The average forward current in D2 and D3 is equal to the output current and therefore a maximum of 20 mA. The peak repetitive forward current in D2 and D3 is equal to twice the output current and therefore less than 40 mA..

The BAT54S comprises two Schottky diodes in a small SOT-23 package and easily meets the current requirements of this application.

8.2.2.8 Positive Charge Pump

8.2.2.8.1 Choosing the Flying Capacitance

A minimum flying capacitance of 330 nF is recommended.

8.2.2.8.2 Choosing the Output Capacitance

Rearranging Equation 10 and inserting the application parameters, we get

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Equation 23. TPS65150 EQN_45_SLVS576.gif

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In this application, a nominal value of 330 nF was used to allow the same value to be used for all charge pump capacitances.

8.2.2.8.3 Choosing the Feedback Resistors

Rearranging Equation 8 and inserting the application parameters, we get

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Equation 24. TPS65150 EQN_47_SLVS576.gif

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Standard values of 1 MΩ and 56 kΩ result in a nominal output voltage of 22.89 V.

8.2.2.8.4 Choosing the Diodes

The average forward current in D4 and D5 is equal to the output current and therefore a maximum of 20 mA. The peak repetitive forward current in D4 and D5 is equal to twice the output current and therefore less than 40 mA.