Functional applications

Four independent output, peak gt; 3A,

1A relay and solenoid valve driver

continuous current capacity

High Improven car injector

The maximum drive resistance of the driver is 1.3

Light drive

The real instantaneous power of each switch Restricted

Power Switch

Switch motor drive

High survival voltage (60 VDC, 80V transient state)

Short -circuit load (grounding and power supply) [123)

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Explanation

Protection LMD18400 is a completely protected quadrilateral high -voltage side. It contains four public drain DMOS N-VCC GT; 35V's overvoltage shutdown channel power switch, each can put A LS TTL/CMOS compatible logic input and 1 ampel load ( gt; 3 amp; ) Switch to the output public positive power supply. The switch is completely lt; 10μA power current is protected in the dormant mode, and is not subject to high voltage, current and temperature. The instantaneous power sensing circuit used for induction discharge 5V output clamping calculation of overvoltage and load multiplication current through each DMOS switch and limit the serial data interface for 11 diagnostic examinations: power to the safe level. The device can be disabled to -open/off the state to produce a dormant state to reduce the power supply -load current opening or short circuit to less than 10 μA. The operating temperature LSTLL/CMOS logic compatible input is controlled by each switch alone. - The power supply voltage is too high Microwire compatible serial data interface has two direct output error signs built -in to provide extensive diagnostic information. This information includes a recovery of the switch status, the output load failure conditions and the heat -stop state. There are also two direct output error signs to provide an immediate general system failure and instructions that the working temperature is too high. The LMD18400 uses a special power supply to encapsulate the dissipated leading leader to reduce the heat resistance of the connected shell to about 20 ° C/W.

Absolute maximum rated value (1) (2)

(1) Absolute maximum rated value indicates that the device may be possible The device may The limit of damage. The work rated value indicates the function of the device, but it is not ensured that specific performance restrictions are not guaranteed. Ensure the standards and test conditions, see electrical characteristics.

(2) If you need military/aerospace special equipment, please contact the Texas Instrument Sales Office/dealer to obtain standardization.

(3) human model; 100 PF discharge through 1.5 k resistance. All citationsExcept for feet (pin 8 and 13, its protection voltage is 1000V) and pin 1, 2, 18, and 19, the protection voltage is 500V.

(4) The maximum power consumption is the function of TJMAX, θJa, and TA, and is limited by heating shutdown. The maximum allowable power to disperse at any ambient temperature is PD (TJMAX -TA)/θJa. If this is scattered, the mold temperature will rise to the final device above 150 ° C will enter the heat shutdown state. For LMD18400, the thermal resistance θJa paired environment is 60 ° C/W. In the case of fully cooling, the maximum continuous power consumption of the packaging is, IDCMAX2 × Ron (maximum) × 4 switches 1A2 × 1.3 × 4 5.2W).

Electrical features

VCC 12V, CCP 0.01 μFD, unless there is another instructions. The thickness limit is suitable for the entire operating temperature range, 25 ° C ≤ TA ≤+85 ° C, and all other limits are TA TJ +25 ° C.

(1) The typical value is tj +25 ° C, which represents the most likely parameter specification.

(2) All limits are 100%production tests performed under+25 ° C. The limits at extreme temperatures are required by relevant and recognized statistical data to perform a prescribed quality control (SQC) method.

Electric characteristics (continued)

VCC 12V, CCP 0.01 μFD, unless there is another explanation. The thickness limit is suitable for the entire operating temperature range, 25 ° C ≤ TA ≤+85 ° C, and all other limits are TA TJ +25 ° C.

(3) Use pulse testing technology. Pulse width lt; 5ms, occupy a duty ratio lt; 1%.

Typical performance features

For all curves, VCC 12V, unless there is another instructions, the temperature is knot temperature

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Basic operation

High -voltage side driving is widely used in automotive and industrial applications, switching the power to the ground reference load. Compared with the low -voltage side driver, the main advantage of using high -voltage side drive is that the protection load is shown in the figure, and the load is unexpectedly short -circuit to the ground Figure 18. The high -voltage side drive can detect short circuit conditions and turn on the power switch to disable the load and eliminate excessive current consumption on the power supply. LMD18400 can control and protect up to four separate ground reference loads.

LMD18400 combines the low -voltage CMOS logic control circuit with the high -voltage DMOS process. Each DMOS power supply is turned onThere are separate opening/off control inputs. When the instruction is turned on, the output of the switch will be connected to the VCC power switch through the maximum resistance of 1.3 (the connection resistance of DMO). The voltage applied on the load depends on the load current and LMD18400. When the switch is closed, except for small leakage currents is often less than 0.01 μA. LMD18400 can be continuously connected to the power supply when drawing. For example, when the car battery is in a dormant state, the current of the power supply is less than 10 μA. This sleep mode is low through enable input (pin 3). In this mode, the power current of the device is often only 0.04 μA. Special low -current consumption spare circuit is used to keep the DMOS switch shut down to eliminate the transient of the power supply voltage of any load (a common problem of the MOS power device). In the dormant mode, all diagnosis and logical circuits are in a non -active state. When the enable input is brought to the logic 1, the switch is switched to standby and prepares to respond to its control input after the delay time (30 μs) is enabled in a short time (30 μs). This delay interval prevent the switch from connected instantaneously. Figure 19 shows the switch control logic.

Each DMOS switch is turned on when its grille driver is about 3.5V higher than its source. Because the power supply of the switch is the load of the output end, the voltage can be obtained very close to the VCC supply potential. Ensure that there is enough voltage to drive the DMO door device built -in charge pump circuit. This circuit is controlled by the internal 300 kHz oscillator, and the external 10NF capacitor is connected from the pins 14 to the ground, generating a voltage of about 20V higher than the VCC power supply voltage. This provides sufficient gate voltage drivers for each switch of the application under the command of the standard 5V logical input level. When driving 1A load current, the opening time of each switch is about 12 μs. This slower switch time helps to reduce the problem of electromagnetic interference (EMI) to minimum high -current level.

Protection circuit

LMD18400 has a wide range of protection circuits. Any power device is essential to prevent excessive voltage, current and temperature conditions. In order to achieve the implementation of the fault safety system, the LMD18400 will automatically disable the load when detecting any overvoltage or over -temperature failure. The range of voltage protection VCC power supply is 0.5V to +60 VDC without any damage to LMD18400. The CMOS logic circuit is a regulator from an internal 5.1V to protect these low -voltage transistors from high VCC potential. However, in order to protect the load connected to the switch output, the overvoltage stops uses a circuit. If the VCC potential exceeds 35V, all switches will be turned off and disconnected. The 35V threshold has a lag of 750 MV to prevent potential oscillation. In addition, the underwriter locking function is built. When VCC is less than 5V, it becomes uncertain whether the logic circuit can keep the switch in the command state. To avoid this uncertaintySexual when VCC drops below about 5V, the switch is turned off. Figure 20 shows that the output is closed during the transient period of 0V to 80V VCC power supply.

LMD18400 design is used to drive all types of loads. When driving the ground sensor load, for example, a relay or thread tube, the voltage on the load will collapse when the power switch is turned off with the magnetic field polarity in the inductor. This will pull the output of the LMD18400 below the ground. This negative transient voltage is restrained at about 5V to protect IC. The clamping motion is not completed, instead of the power supply DMOS switch immediately re -connected to guide the electric sensor current cutting power, as shown in Figure 21.

When the output inductor generates negative voltage, the gate of the DMOS transistor is restrained at 0V.AT 3.5V, and the power supply of the power supply equipment is small than the grid to make the power supply. The switch is connected again. Under this negative transient condition, the power limit circuit of the protection switch is kept 0V due to the gate. The maximum current during this clamp interval is equivalent to the current ON through the electrical sensor's current should be kept below 1A. Another problem in this interval and the size of the sensor load and the time required for power off. If the electrical sensor is greater, the additional power consumption may cause the mold temperature to exceed the heat shutdown limit. If this happens, all other switches will be closed immediately (see the heat management part).

Power limit

LMD18400 uses a real instantaneous power limit circuit instead of simple current limit to protect each switch. This provides a higher transient current capacity, while still maintaining a safe power consumption level. The power consumption of each switch (the product of the leakage source and the output current, VDS × IOUT) is continuously monitored by changing the grid voltage and the diverter resistance and limited to the 15W switch. Basically, the pitch resistance will be as low as possible until 15W is dissipated. Maintain 15W, increase the power resistance, and reduce the load current. This will cause the output voltage to decrease. For the resistance load, the output voltage during power limit is:

As shown in Figure 22, this provides the maximum transient current and leakage source voltage characteristics.

The steady -state current of the load is encapsulated power consumption, ambient temperature, and switching resistance. The characteristics shown. This dynamic current of the switch is limited when the driver light and large capacitor load are beneficial. When the lamp was connected for the first time, a large wave current was needed, which was about 10 times cold filaments of the normal working current. LMD18400 will limit the initial current to the level of 15W in the switch. As the voltage on the filament -pre -heating light, the voltage on the switch can be reduced so that more current can completely light up the light. In the case of limited incentives, the life of the lamp load is significantly increased. picture23 shows the soft turn on the lamp load. As the load voltage increases, the principle of increasing output current also allows large capacitors to compared with drivers with a fixed 1A current, the LMD18400 drive is faster to protect the load charging. Figure 24 shows the output response when the driver is driven.

Heat protection

Continuously monitor the mold temperature of LMD18400. If any condition causes the mold temperature to rise to+170 ° C, all power switches are automatically closed to reduce power consumption. It is important to recognize that the heat shutdown affects all four switches at the same time. In other words, if it is just a switch load that is enough to heat the mold to the hot turnout threshold, all other switches will turn off regardless of its power consumption conditions. When all switches will be reopened, the mold temperature has been cooled to about+160 ° C. Until the high temperature compulsory condition remove the switch, the circulation will be turned on and closed, so as to maintain the average mold temperature+165 ° CLMD18400 will send a signal with a high temperature (see diagnosis) through multiple diagnostic output signals.

Diagnosis

LMD18400 has a wide range of circuit diagnostic information reporting functions. Using this information can produce systems with intelligent feedback with switching status and load failure conditions in order to perform fault exclusion. All diagnostic information is included in a 11 -bit word. These data can be series from LMD18400, as shown in Figure 25. Differential register and diagnostic data are loaded parallel. When the chip is selected for serial mode, as long as the chip is switched to select 1 mode logic 0. The data output cable (pin 8) comes from 5.1V regulator voltage setting logic 1 output. The pin has the ability to have a low current source, so any load on the pin will reduce logic 1 output levels at least 2.4V under 360 μA load. The data interface is compatible with micrine, because the data outputs the clock from the decrease of the LMD18400 along the clock, and the timing is used in the control micro -processor that rises along the rising edge. Any amount of device can share a public data output cable, because the data output tube foot is kept in a high impedance (three state) state until the chip selection input is reduced to select the device. After the chip selection becomes lower, there is a short data that needs to set the time interval (500 NS min). This is based on the data output line of the first data level that allows the information to allow information to enter the controller before the first rising clock edge. When all 11 -bit diagnostic data are removed, the data output enters the logic 1 level until the chip is selected to return to the high -end.

FIG. 25 also shows the importance of diagnostic data bit. The first 4 digits represent the output load error condition, each channel is one consecutive (see the load error detection). Bit 5 to 8 provides the command to read/off the command of each switch. One of the unique parts of LMD18400 is that it provides early warning with high work temperature. If the mold temperature exceeds+145 ° C, the bit 9 will be set to logic 0Essence According to this information, the system can be programmed to take corrective measures, which may be turned off at the LMD18400 to turn off the specific load running normally (not in the hot stack state). If the warning is ignored, the device continues to rise at temperature, and the heat shutdown circuit will start working when the mold temperature is+170 ° C. If the occurrence of data stream 10 will be set to logic 0, and all outputs in the indicator device are cut off. The final data bit, bit 11 indicates the overvoltage conditions on the VCC power supply (VCC greater than 35V), and once again indicates that all drivers are closed.

The diagnostic data may be read regularly by the controller, or it reads instructions to determine any system failure when the general system error occurs. The general indication of the fault is output by the error sign (pin 13). As long as any type of error is detected, the pin will become lower. There is a built -in delay from detecting the error to the pin 13 of about 75 μs. This is to help the mask's short duration error conditions, such as the driver's high -capacitance load ( gt; 2μF). The light load may produce a short -circuit loading error of hundreds of milliseconds when it is turned on, and this error should be ignored.

The output pin of the error sign is an open drain transistor. It requires a positive voltage of a pull -up resistor. Generally speaking, this type of pulling is the same 5V for the same 5V For power, it will be biased to enable input and any other external input logic circuit. The error signs of several LMD18400 packaging can be connected with a pull -up resistor to provide a comprehensive system error instruction. Once the error is detected, each one can be asked to obtain the diagnostic information to determine the source of the fault. The second direct output error sign is used to indicate the heat shutdown (pin 17). The low sign of this event provides the temperature of the molding mold immediately that the mold has reached+170 ° C, and the driver of all four switches has been deleted. The output is pulled to the internal 5.1V logical regulator through a small (5μA) current source. Therefore, it is recommended to use the buffer on the pin.

One of the useful features of pin 17 is that it can also be used as a stop input. Put this needle low and turn off all the drivers immediately, control the logic and the diagnostic circuit as if reaching the hot turnover temperature. This can be disabled to disable the load when designing the fault security system when any external detection system failure. However, diagnostic logic cannot distinguish the fact that the normal heat shutdown or pin 17 is driven low. Like this, various switch errors and ultra -temperature instructions will be reported in the diagnostic data stream. FIG. 26 illustrates the pins 17 as the output heat clearance logo and the input switch that is only turned off. Directly tied needle 17 to+5V to prevent the internal heat shutdown circuit disabled switch. However, for the purpose of reliability, it is not recommended to do this, because there will be no maximum limit mold temperature. Operations about these direct output error signsSummary, see the real value table. One important feature of the load error detection of LMD18400 is that the load connection that can detect openings or short -circuit. Figure 27 illustrates the detection circuit used by each drive.

The voltage of the voltage comparator monitor the load, and compare it with the fixed 4.1V reference level. When the switch is broken, there should be no voltage between the ground reference load. In this case, K #8486 connected to VCC internally 50; the resistor will provide a small amount of current to the load. If the load resistance is large enough to generate a voltage greater than 4.1V, the switch will display the opening load error. When the maximum value is turned on, the load resistance that does not generate an open load error can pass:

In order to make this open load error threshold more reasonable, it can be exported from output to VCC power supply Essence In addition, when the switch is instruction closed, if the load is short -circuited to the VCC power supply, the circuit will once again indicate the error. When a switch is connected, there will be a voltage potential close to VCC on the load. If the output voltage is lower than the 4.1V threshold, the error will be reported again, indicating that the load is short -circuited to the ground, or the driver is at the power limit, and no output voltage is closer to the VCC. When the switch is connected to the CAN, the minimum load resistor who does not produce a short -circuit load error:

FIG. 28 shows the load resistance range indication of normal operation, opening load and short -circuit load or power limit.

Hot Management

It is particularly important to consider the total power consumed by all four switches in the LMD18400. Any switch combination of any driver load will cause the mold to increase the temperature. If the mold temperature reaches a heating threshold with+170 ° C, all switches will fail. Carefully calculate the total power consumption in the worst situation required for any time, and provide sufficient heat dissipation to prevent this from happening. The LMD18400 packaging has a special lead framework that helps each side of the heat dissipation packaging through two ground pins. The thermal resistance (θJC) from the shell is about 20 ° C/W. The heat resistance (θJa) from the surrounding is about 60 ° C/W without any heat dissipation. FIG. 29 illustrates how to design the copper foil of the printing circuit board to heat the heat and reduce the thermal resistance of the overall pairing environment. The power consumption of each switch is equal to:

RON is the connection resistance of the switch (maximum 1.3 ) (4) Before the power loss reaches the maximum limit of 15W, these equations are still established. In the following cases, the 15W power limit threshold will be reached:

The induction load will generate additional power consumption when it is closed. Figure 30 shows the voltage and current waveform of the ideal sensor load.

When opening, the worst case is:

The inductor steady -state power current of each power switch should be kept below 1A.关断时的额外功耗，当电感器断电时电感器夹持至 5V，可通过以下方式找到：

对于时间间隔， TCLAMP. This is the time required for the electrical sensor current to fall to zero:

The size of the inductor will determine the duration of this additional power interval. Although the peak current is kept below 1A, within this time interval, the switch will see the voltage VCC+5V unable power restriction protection on it. If the sensor is too large, the time interval may be long enough to heal the mold temperature of+170 ° C, so as to close all other loads on the package.

The total average power consumption of the inductive load throughout the entire switching cycle is:

Due to the common cutting of all loads for the heat shutdown, the heat time constant of the package became a problem. Figure 31 shows that the time required for heating molds to turn on the heat shutdown starts with the initial knot temperature+25 ° C. The packaging power consumption gradually increases the use of the PC plate layout for measurement. The thermal resistance from the connector to the environment is about 35 ° C/W. Of course, the smaller the heat dissipation, the faster the heat shutdown speed of the power switch.