Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

TPS767D301 is the latest dual-channel low-dropout adjustable voltage Regulator from TI. This article introduces its main features, pin functions, internal structure, working principle, adjustable output principle and typical power supply circuit connection in detail. A TMS320F2812DSP power circuit based ON TPS767D301 is presented. At present, this circuit has been successfully applied to the DSP application system designed by the author and it works stably and reliably.

Authors: Zhang Yunan, Feng Zhihua, Wang Xiaofeng

1 Introduction

Since the American TI company launched the general programmable DSP chip, DSP technology has been developed by leaps and bounds, but the power supply design of DSP has always been an important part of the design of DSP application systems. TI’s DSP family generally requires an independent core power supply. And IO power supply, because DSP has to undertake a large amount of real-time data calculation in the system, because in its CPU, the frequency switching of components will greatly increase the system power consumption, so reducing the internal CPU power supply Voltage of the DSP is undoubtedly reducing the system power consumption. One of the most effective methods. For example, the core voltage of TMS320F2812DSP is 1.9V, and the IO voltage is 3.3V; therefore, traditional Linear regulators (such as 78XX series) can no longer meet the requirements. In the face of these requirements, TI has introduced some dual low-dropout power regulators , Namely LowDropRegulator, in which TPS767D301 is its recently launched dual low-dropout (and one of them is also adjustable) voltage regulator, very suitable for power supply design in DSP application systems, based on this, this article has carried out a detailed description of the power supply chip Introduced and designed the power supply circuit of TMS320F2812DSP based on TPS767D301.

2 Main features and pin functions of TPS765D301

TPS767D301 is a dual-channel low-dropout power regulator newly launched by TI. It is mainly used in DSP designs that require dual power supply. Its main features are as follows:

◆With dual outputs with independent power supply, one fixed output voltage is 3.3V, and the other output voltage can be adjusted, the range is 1.5-5.5V;
◆The range of each output current is 0-1A;
◆The voltage difference is proportional to the output current, and when the maximum output current is 1A, the maximum voltage difference is only 350mV;
◆It has an ultra-low typical quiescent current (85μA), when the device is in an invalid state, the quiescent current is only 1μA;
◆Each regulator has an open-drain reset output, and the reset delay time is 200ms;
◆28-pin TSSOPPowerPAD package form can ensure good power consumption characteristics;
◆The operating temperature range is -40℃-125℃, and each regulator has a temperature automatic shutdown protection function.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Figure 1 is a TPS767D301 pin layout diagram, the functions of each pin are listed in Table 1.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

2.1 Internal structure and working principle

The internal principle block diagram of TPS767D301 is shown in Figure 2. Figure 2 (a) is the internal principle diagram of the 3.3V fixed output regulator, and Figure 2 (b) is the internal principle diagram of the adjustable output regulator, which can be seen from Figure 2. , And the device is composed of error Amplifier, voltage comparator, reference voltage (1.1834V), sampling Resistor network, 200ms delay circuit and PMOS regulator. When the regulator is working, ensure that the enable terminal EN is low level. After the input voltage V1 is added to the IN terminal, the output terminal OUT will have a voltage output. The sampling Resistor is used for the network to sample the output voltage to match the reference voltage (1.1834V). ) For comparison, when the output voltage Vo is lower than the reset lower threshold level VIT-, the reset terminal RESET immediately becomes low. After that, even if V0 quickly returns to higher than the reset upper threshold level VIT+, it is still valid , But the low-level pulse will be delayed by 20ms. Figure 3 is the timing diagram of the regulator, where Vres is the minimum output voltage when the reset pulse is valid. The two regulators can be powered separately and output separately, or they can be powered together.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Table 2 lists the limit parameters of TPS767D301.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

3 Adjustable output principle and circuit connection method of TPS767D301

The output of the adjustable voltage regulator in TPS767D301 can be adjusted within the range of 1.5-5.5V. This adjustment is mainly achieved by connecting an external resistor sampling network. The connection method is shown in Figure 4, and the input should be added in the design. Last 0.1-0.047μF ceramic Capacitor, and add an electrolytic capacitor with a size of 10-30μF and ESR between 60mΩ-1.5Ω to the output terminal to smooth the output voltage, and its open-drain reset output terminal should also It is connected to the positive voltage through a pull-up resistor. When the output voltage is lower than the reset threshold level, the reset signal is output at low level. In fact, the reset output terminal can also be left unused.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

The adjustable output voltage can be determined by the following formula:

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Among them: the value of Vref=1.1834 VR1 and R2 should ensure that the current passing through them is about 50μA, and their value cannot be too large or too small. Generally speaking, it is recommended to choose R2=30.1KΩ, which can pass ( 1) The formula for the value of R1 is:

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

For typical voltage output, the values ​​of R1 and R2 are listed in Table 3.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

4 TMS320F2812 power supply circuit based on TPS767D301 low dropout regulator

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

In order to improve reliability, the external pure +5V power input is filtered by a ferrite bead and then enters the power chip, and the enable terminal of the 3.3V fixed output regulator is grounded, so that it will be established when the power is turned on. Starting with a 3.3V voltage, the 3.3V can make the Transistor 2N2222 saturate and conduct, thereby pulling the enable end of the adjustable output regulator to a low level, and then set a suitable sampling resistor network to make the output 1.9V, thereby solving Two different voltage outputs and their power-on sequence problems. In addition, the 1.9V and 3.3V digital voltages are filtered by ferrite beads L2 and L3, respectively, to form a 1.9V analog power supply and a 3.3V analog power supply. After that, connect the reset output terminals of the two regulators in parallel and connect to the reset output terminal of the DSP through a pull-up resistor to 3.3V. In this way, once any voltage of 1.9V or 3.3V drops below its threshold voltage, There will be a 200ms low-level pulse to reset the DSP.

5 concluding remarks

TPS767D301 is the latest dual-channel low-dropout adjustable voltage regulator from TI. This article introduces its main features, pin functions, internal structure, working principle, adjustable output principle and typical power supply circuit connection in detail. A TMS320F2812DSP power circuit based on TPS767D301 is presented. At present, this circuit has been successfully applied to the DSP application system designed by the author and it works stably and reliably.

Authors: Zhang Yunan, Feng Zhihua, Wang Xiaofeng

1 Introduction

Since the American TI company launched the general programmable DSP chip, DSP technology has been developed by leaps and bounds, but the power supply design of DSP has always been an important part of the design of DSP application systems. TI’s DSP family generally requires an independent core power supply. And IO power supply, because DSP has to undertake a large amount of real-time data calculation in the system, because in its CPU, the frequency switching of components will greatly increase the system power consumption, so reducing the internal CPU power supply voltage of the DSP is undoubtedly reducing the system power consumption. One of the most effective methods. For example, the core voltage of TMS320F2812DSP is 1.9V, and the IO voltage is 3.3V; therefore, traditional linear regulators (such as 78XX series) can no longer meet the requirements. In the face of these requirements, TI has introduced some dual low-dropout power regulators , Namely LowDropRegulator, in which TPS767D301 is its recently launched dual low-dropout (and one of them is also adjustable) voltage regulator, very suitable for power supply design in DSP application systems, based on this, this article has carried out a detailed description of the power supply chip Introduced and designed the power supply circuit of TMS320F2812DSP based on TPS767D301.

2 Main features and pin functions of TPS765D301

TPS767D301 is a dual-channel low-dropout power regulator newly launched by TI. It is mainly used in DSP designs that require dual power supply. Its main features are as follows:

◆With dual outputs with independent power supply, one fixed output voltage is 3.3V, and the other output voltage can be adjusted, the range is 1.5-5.5V;
◆The range of each output current is 0-1A;
◆The voltage difference is proportional to the output current, and when the maximum output current is 1A, the maximum voltage difference is only 350mV;
◆It has an ultra-low typical quiescent current (85μA), when the device is in an invalid state, the quiescent current is only 1μA;
◆Each regulator has an open-drain reset output, and the reset delay time is 200ms;
◆28-pin TSSOPPowerPAD package form can ensure good power consumption characteristics;
◆The operating temperature range is -40℃-125℃, and each regulator has a temperature automatic shutdown protection function.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Figure 1 is a TPS767D301 pin layout diagram, the functions of each pin are listed in Table 1.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

2.1 Internal structure and working principle

The internal principle block diagram of TPS767D301 is shown in Figure 2. Figure 2 (a) is the internal principle diagram of the 3.3V fixed output regulator, and Figure 2 (b) is the internal principle diagram of the adjustable output regulator, which can be seen from Figure 2. , And the device is composed of error amplifier, voltage comparator, reference voltage (1.1834V), sampling resistor network, 200ms delay circuit and PMOS regulator. When the regulator is working, ensure that the enable terminal EN is low level. After the input voltage V1 is added to the IN terminal, the output terminal OUT will have a voltage output. The sampling resistor is used for the network to sample the output voltage to match the reference voltage (1.1834V). ) For comparison, when the output voltage Vo is lower than the reset lower threshold level VIT-, the reset terminal RESET immediately becomes low. After that, even if V0 quickly returns to higher than the reset upper threshold level VIT+, it is still valid , But the low-level pulse will be delayed by 20ms. Figure 3 is the timing diagram of the regulator, where Vres is the minimum output voltage when the reset pulse is valid. The two regulators can be powered separately and output separately, or they can be powered together.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Table 2 lists the limit parameters of TPS767D301.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

3 Adjustable output principle and circuit connection method of TPS767D301

The output of the adjustable voltage regulator in TPS767D301 can be adjusted within the range of 1.5-5.5V. This adjustment is mainly achieved by connecting an external resistor sampling network. The connection method is shown in Figure 4, and the input should be added in the design. Last 0.1-0.047μF ceramic capacitor, and add an electrolytic capacitor with a size of 10-30μF and ESR between 60mΩ-1.5Ω to the output terminal to smooth the output voltage, and its open-drain reset output terminal should also It is connected to the positive voltage through a pull-up resistor. When the output voltage is lower than the reset threshold level, the reset signal is output at low level. In fact, the reset output terminal can also be left unused.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

The adjustable output voltage can be determined by the following formula:

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

Among them: the value of Vref=1.1834 VR1 and R2 should ensure that the current passing through them is about 50μA, and their value cannot be too large or too small. Generally speaking, it is recommended to choose R2=30.1KΩ, which can pass ( 1) The formula for the value of R1 is:

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

For typical voltage output, the values ​​of R1 and R2 are listed in Table 3.

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

4 TMS320F2812 power supply circuit based on TPS767D301 low dropout regulator

Application scheme of dual low dropout power regulator based on DSP chip MS320F2812

In order to improve reliability, the external pure +5V power input is filtered by a ferrite bead and then enters the power chip, and the enable terminal of the 3.3V fixed output regulator is grounded, so that it will be established when the power is turned on. Starting with a 3.3V voltage, the 3.3V can make the Transistor 2N2222 saturate and conduct, thereby pulling the enable end of the adjustable output regulator to a low level, and then set a suitable sampling resistor network to make the output 1.9V, thereby solving Two different voltage outputs and their power-on sequence problems. In addition, the 1.9V and 3.3V digital voltages are filtered by ferrite beads L2 and L3, respectively, to form a 1.9V analog power supply and a 3.3V analog power supply. After that, connect the reset output terminals of the two regulators in parallel and connect to the reset output terminal of the DSP through a pull-up resistor to 3.3V. In this way, once any voltage of 1.9V or 3.3V drops below its threshold voltage, There will be a 200ms low-level pulse to reset the DSP.

5 concluding remarks

TPS767D301 is the latest dual-channel low-dropout adjustable voltage regulator from TI. This article introduces its main features, pin functions, internal structure, working principle, adjustable output principle and typical power supply circuit connection in detail. A TMS320F2812DSP power circuit based on TPS767D301 is presented. At present, this circuit has been successfully applied to the DSP application system designed by the author and it works stably and reliably.

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