Features

* 5V ± 2%output

* Low 70 micro -static current

* Active reset

* Input of inputs controlled by opening/level and activation/dormant mode

* 100mA output current capacity [123 ]

*

Fault protection+60V peak transient voltage-15V reverse voltage short circuit heat overload

*

Low-reverse current (output to input) [ 123] Program package option

CS8101

is a precise 5V micro -power regulator, which has a very high Low static current (at 100 micro -'an loads 70 Weire). The 5V output accuracy is within ± 2%, providing a 100mA load current. The typical voltage voltage voltage is only 400 medium voltage microprocessor control logic includes input and activation. The combination of this low static current, excellent regulator performance and control logic makes the CS8101 very suitable for any battery operation and microprocessor control equipment.

The activation circuit includes lagging and working normally under the output voltage as low as 1V. If the output voltage exceeds 200mV, the reset function is activated during the power -on order or during the normal working period. Logical compatibility input allows users to place the regulator in the shutdown mode. In this mode, the regulator only absorbs the typical static current of 20 Weian. The regulator can prevent the battery from reverse, short -circuit, overvoltage and heat overload. This device can withstand load uninstallation of transient and suitable for use in the car environment.

CS8101 is equivalent to the national semiconductor LP2951 series low -current regulator.

Figure

Circuit description

Voltage benchmark and output circuit

output level protection

] The output level is protected by overvoltage, short -circuit and thermal discharge conditions (Figure 1).

If the input voltage rises to more than 30V (such as load uninstall), the output will be closed. This response to protect the internal circuit, enabling integrated circuits to withstand unexpected voltage transients.

If the connection temperature of the power device exceeds 180 #223; C (typical values), the load current capacity will be reduced to prevent heat overload. This thermal management function is an effective means to prevent overheating molds, because load current is the main heat source of integrated circuits.

The regulator control function

CS8101 contains two microprocessors compatible control functions: enable and reset (Figure 2).

Enable function

Enable function to open and turn off the output transistor. When the voltage on the wire is more than 1.4V, the output is closed through the transistor to make the high impedance facing the load. The integrated circuit will keep the sleep mode and consume only 50A until the voltage on the input drops below the enable threshold.

Reset function

When the integrated circuit is powered, generates reset signal (low voltage) until Vout is regulated 250 millivolttime range of the output voltage, or when VOUT loses adjustment, and low is low Adjust the output voltage 300 millivolo. The function contains 50mv lag, which oscillated with minimumization.

The resetting output is the opening of the circuit collector NPN transistor, which is controlled by the low -voltage detection circuit. The circuit is independent of the rest of the IC in terms of function, thereby ensuring that the reset signal is valid for VOUT as low as 1V as low as 1V.

The external RC network on the lead (Figure 3) provides sufficient latency for most microprocessor -based applications. You can use the following formulas to select the RC value:

In the formula: rrst delay resistor;

RIN μP port impedance;

RTOT rrst is parallel with RIN;

CRST delay capacitor;

tdlay required delay time;

VRST vsat of the wire (0.7V at the time of opening);

vt threshold.

Application description

The circuit shown in FIG. 4 allows microprocessors to control its power CS8101 regulator. The I/O ports and switch ports on P are used to drive the base of Q1. When Q1 is driven to saturated, the voltage on the capacity is reduced to lower its threshold. The output of the regulator has been enabled. When the driving current is removed, the voltage on the wire is increased, the output is closed, and the IC enters the dormant mode. In this mode, the maximum current is 50 A.

By coupling these two controls with Enable Lead, the system increases flexibility. Once the system is running, as long as the I/O port continues to drive Q1, the status of the switch is irrelevant. Once the switch is turned on, the microprocessor can turn off your power by extracting the driver current. This software control on port I/O allows microprocessors to complete key management functions before power off.

Table 1 summarizes the logic option.

The I/O port of the microprocessor usually provides 50 A to Q1Essence In the car application, the switch is connected to the ignition switch.

Stability Consider

Output or compensation capacitance can help determine the three main features of linear regulators: start delay, load transient response, and circuit stability.

The value and type of capacitor should be based on cost, availability, size and temperature limit.容 or aluminum electrolytic capacitors are the best, because the re -melting of the electric slag is almost zero -zero -film or ceramic capacitor can cause unstable. Aluminum electrolytic capacitors are the cheapest solutions, but if the circuit works at low temperature (-25 ℃ ～ -40 ℃), the value of the capacitor and ESR will change greatly. The data table of capacitor manufacturers usually provides this information.

The output capacitance value shown in FIG. 5 should apply to most applications, but it is not necessarily an optimized solution.

To determine the acceptable value of the COUT in a specific application, please start with the electrical container of the recommended value and be committed to the alternative part with lower development costs.

Step 1: Place a complete circuit with a recommended value capacitor in an environment room with a minimum prescribed working temperature, and monitor the output with a oscilloscope. Ten -year boxes connected to the capacitor will simulate the higher ESR of aluminum capacitors. Putting the ten -year box outside the test box, the small resistance increased by the longer lead can be ignored.

Step 2: When the input voltage reaches the maximum value, slowly increase the load current from zero to full load, and at the same time observe whether the output is any oscillation. If the oscillating is not observed, the capacitor is large enough to ensure the stable design under steady condition.

Step 3: Use ten years to increase the ESR of the capacitor from zero, and change the load current until the oscillation occurs. Records cause maximum oscillating load current and ESR values. This indicates the worst load conditions of the regulator at low temperature.

Step 4: Keep the worst load conditions set in step 3 and change the input voltage until the oscillation increases.

This point represents the input voltage conditions in the worst case.

Step 5: If the capacitor is sufficient, repeat steps 3 and 4 for the next smaller capacitor. Smaller capacitors usually cost lower and occupy less board space. If the output is oscillated within the expected working conditions, the next larger standard capacitance value is repeated step 3 and 4.

Step 6: Test the transient response of the load by switching the load of different frequencies to simulate its actual working environment. Change ESR to reduce ringing.

Step 7: Take the device from the environment room and heat the IC with heating gun. Change the load current according to the instructions in step 5 to test whether there are any oscillations.

Once found the minimum capacitor value with the maximum ESR, a safety factor should be added to consider any changes in the performance of the capacitor and the performance of the regulator. Most high -quality aluminum electrolytic capacitorsThe tolerance of the device is -20%, so the minimum value discovered should be increased by at least 50%to allow the tolerance to add changes at low temperature. The ESR of the capacitor should be less than 50%of the maximum allowed ESR in the above step 3.

Calculation of the power consumption of a single output linear regulator

The maximum power consumption of a single output regulator (Figure 6) is:

Among them: VIN (MAX) is the maximum input voltage, VOUT (min) is the minimum output voltage, iOUT (MAX) is the maximum output current of the application, and IQ is the static current iOUT (maximum value) consumed by the regulator.

Once you know the value of the PD (MAX), you can calculate the maximum allowable value of RQJA:

Then you can put the value of the RQJA value and the data table of the package of the data table. Compare the values in the part. The encapsulation of the calculated values in the RQJA less than the equivalent 2 will keep the mold temperature below 150 ° C.

In some cases, there is no heat that is encapsulated enough to distribute ICs and requires an external radiator.

The radiator

The heat sink effectively increases the surface area of the packaging to improve the flow of heat from integrated circuits to the surrounding air.

Each material in the heat flow between the integrated circuit and the external environment will have heat resistance. Like the series resistance, the value of these resistors determines the value of RQJA:

In the formula: RQJC pair -pair shell thermal resistance, RQCS thermal resistance from the shell to the radiator, RQSA The heat resistance of the radiator to the environment.

RQJC appears in the Package part of the data table. Like RQJA, it is also a function of the package type. RQCS and RQSA are functions of encapsulation type, radiator and interface between them. These values appear in the radiator data table of radiator manufacturers.

Packaging size unit: mm (inch)

Packaging heat data

The surface installation is narrow -narrow installation narrow installation Body (D); 150 mil width

Surface stickers (DW); 300 mil width

Packaging specification