General description

LP4950C and LP4951C are very low static current (75μA typical values) and low voltage deviation voltage (typical. Light load at 40 millivolves, at 100 mAh). They are the ideal selection system for battery power supply. In addition, the static current LP4950C/LP4951C will only increase slightly when the power is lost, thereby extending the battery life. The LP4950C in the popular 3 needle to the 92 packaging is compatible with the old 5V regulator. The 8 -line LP4951C provides plastic surface installation packaging and provides additional system functions. One of this characteristic is the output of the error logo, which warns the low output voltage, usually caused by the battery of the input end. It can be used for power -on reset. The second feature is logical compatibility closure input, which makes the regulator open and close. In addition, parts can also be bundled with 5V output or by programming from 1.24V to 29V external resistors. The carefully designed LP4950C/LP4951C will contribute all to the wrong budget. This includes a strict first -letter tolerance (typical value of 0.5%), load and line adjustment very good (typical value 0.05%) and extremely low output voltage temperature coefficients, so that the component is used as a low -power voltage reference.

Features

High -precision 5V guaranteed 100mA output

Extremely low static current

Low voltage difference voltage

Extreme load and line adjustment

Extremely low temperature coefficient

It is used as a regulator or reference

Only 1 μF can be stable

current and heat limit

Only LP4951C version

Error sign warning output loss

Logical control electronic shutdown

Output can be programmed 1.24 to 29V

Frame diagram

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[[ 123] Application

Absolute maximum rated value (Note 1)

Input power voltage 0.3 to+30V

[

123] The input voltage of the shutdown, the output of the error comparator

Voltage (Note 9) 0.3 to+30V

Feedback input voltage 1.5 to+30V (Note 9) (Note 10)

Limited internal power consumption

Jiexin (TJ)+150 ; C

Environmental storage temperature 65 ; to+ 150 ; C

Welding staying time, temperature

Wave

Infrared gas

4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds, 4 seconds.260 degrees Celsius

10 seconds, 240 degrees Celsius

75 seconds, 219 degrees Celsius

ESD to be determined

working rated value (Note 1)

] The maximum input power supply voltage 30V

Concluding temperature range (Note 8)

LP4950C, LP4951C 40 ; C to 125 ; C

electrical characteristics (Note 2)

electrical characteristics

Note 1: The absolute maximum fixed value refers The equipment may be damaged. The operating rated value refers to the guarantee of the device operation. Running rated values do not mean guarantee performance restrictions. For guarantee performance restrictions and related test conditions, please refer to the electrical characteristic table.

Note 2: The guarantee value of the guarantee vehicle identification number (VIN) is 1, unless it appears on the black body No. 1, it should be applied to all the restricted value of the number of restricted values represented by Black Body. The limit in normal types is suitable for TA TJ 25 ; C. The additional conditions of the 8 -needle version are feedback related to VTAP, the output is connected to the induction (VOUT 5V), and VSHUTDOWN ≤ 0.8V.

Note 3: Guarantee and 100%production test.

Note 4: Guarantee but not 100%production test. These limits are not used to calculate the level AQL level.

Note 5: The differential voltage measured under the output voltage difference of 100 millivoltors is 1 millivolo. In the case of a very low programming output voltage, the minimum input power supply voltage 2V (exceeding temperature 2.3V) must be considered.

Note 6: The threshold of the comparator is expressed by the voltage difference at the feedback end of the nominal reference voltage measured at VIN. (R1+R2)/R2 output voltage is 5V. When the output voltage drops 95 mv x 5V/1.235V 384, the error output guarantees low millions It is usually less than 5%lower than the nominal value, which is guaranteed to be 7.5%.

Note 7: VREF≤VOUT ≤ (vin 1V), 2.3V ≤Vin ≤ 30V, 100μA≤il≤100mA, TJ≤TJMAX.

Note 8: The connection to environmental thermal resistance is as follows: To-92 package is 180 ; C/W and 160 ; C/W, with 0.40-inch and 0.25-inch lead to-92 The packaging is circuit board (PCB), and the molding SOP(M) 160 ; C/W. The thermal resistance of the above M packaging is applied to the welding package directly to the PCB.

Electric characteristics (continued)

Note 9: may exceed the input power voltage.

Note 10: When used in a dual power supply system, when the output is seen to return to the negative power supply, the output voltage should be clawed by the diode.

Note 11: VSHUTDOWN ≥ 2V, vin≤30V, vout 0, feedback pins are connected to VTAP.

Note 12: The output or reference voltage temperature coefficient is defined as the worst case, the voltage change is divided by the total temperature range.

Note 13: Thermal regulation refers to the change of the output voltage at T times after the power dissipation changes are applied, excluding the effects of load or line adjustment. The technical specifications are suitable for VIN 30V (1.25W pulse) under 50 mA load pulses, T 10MS.

Note 14: Under the constant knot temperature, use a low -occupied pulse test measurement and adjustment. The output voltage changes caused by thermal effects are included in thermal regulation specifications.

Note 15: LP4951C's line adjustment is tested at 150 ° C, IL 1 MA. For IL 100 μA and TJ 125 ; C, the design guarantee line adjustment is 0.2%. Typical performance characteristics of line adjustment and temperature and load current.

典型性能特征

[123 ] Program prompt

External capacitors

The output requires 1.0μF (or larger) capacitors and stability grounding under 5V or higher output voltage. In the lower output voltage, more capacitors are needed. Part of this capacitor will oscillate. Most types of tadpoles or aluminum electrolytic work well here, and even film types can be used, but it is not recommended for cost reasons. Many alum electrolyte electrolytes are 30 ; The important parameter of the capacitor is that ESR is about 5 or smaller, and the resonance frequency is higher than 500 kg. The value of this capacitor can increase without restrictions. The smaller the output current, the smaller the output capacitance requirements. The capacitor can be reduced to 0.33 μF when the current is lower than 10 mA, and the current is 0.1 μF below 1 mAh. When the voltage is lower than 5V, the 8 -needle version is used at a lower gain. In the worst case, the 100 MA load (output pair of feedback short circuit) A should use 3.3 μF (or higher) capacitors when the output of 1.23V output. Not with many other regulatorsIn the same way, the LP4950C will continue to have a stable and no load adjustment internal pressure. This is especially important in CMOS to maintain an activity application. When the output voltage of the LP4951C version with an external resistor is set, it is recommended to have a minimum load of 1 μA. Place 0.1 μF capacitors/LP4951C input ground from LP4950C. LP4951C feedback terminal (pin 7) mixed capacitors can cause unstable. When a high -value external resistance is used to set the output voltage. Add a 100PF capacitor between the output and feedback and increase the output capacitor to at least 3.3 μF to fix this problem.

error detection comparator output

When the LP4951C output exceeds the adjustment range of about 5%. This number is the built -in offset of the comparator approximately 60 millivols except 1.235 reference voltage. (Reference to the square diagram in front of the data table) The level remains ""below the normal value of 5%"" regardless of the programming output voltage of 4951C. For example, for 5V output, the markup level of the error sign is usually 4.75V or 11.4V output for 12V. A low input voltage, current limit or heat limit may occur beyond the specified situation. The following figure 1 gives the timing diagram signal and voltage voltage output voltage of the description error is LP4951C input up and down. The error signal becomes effective (low) about 1.3V input. It becomes high at about 5V input (input voltage when vout 4.75V). Since

The drop voltage of LP4951C depends on the load (the typical performance characteristics of the curve in the medium), and the input voltage checkpoint (about 5V) will change with the load current. The output voltage trigger point (about 4.75V) does not change with the load. The error comparator has an external pull -out -output output. This resistor may return to the output or other power supply voltage according to the system requirements. When determining this value, please note that when the output is set to absorb 400 μA, the absorption current will increase the battery consumption when the battery is insufficient. The recommended value range is 100k to 1m . The resistance is not needed if this output is not used.

When Vin≤1.3V, the error signs become high impedance, and the error sign voltage rises to its pull voltage. Use VOUT as a pull -down voltage (see Figure 2) instead of the external 5V power supply, which will be maintained in this case, and the error sign voltage is lower than 1.2V (typical value). Users may want to use equivalent resistors (10 k ) to ensure that there are low level logic signals under any failure, and effective high -logic levels are still allowed during normal operation periods. Essence

Output voltage programming (LP4951C)

LP4951C can use its internal pins and bundle 5V to connect the needle 1 (output) with the needle 2 (induction) to achieve the division of the pinch, and sell Together. Alternatively, it can be programmed to maximize any output voltage between the 1.235V reference voltage and 30V voltage. As shown in Figure 2, a resistor needs a resistor. The complete equation of the output voltage is

. VREF is nominal 1.235 reference voltage, IFB is feedback pin bias current, nominal 20 mAh. When the minimum is recommended to be 1 μA, a upper limit will generate a cap. If the value of the regulator R2.2Ω must be vacuum (a situation that often appears when CMOS stands standby). IFB will produce a typical error in VOUT, which can eliminate the fine -tuning R1 by fine -tuning at room temperature. In order to be more accurate, select R2 100K, reduce the error to 0.17%, and increase the current current of the resistor program to 12 μALP4951C. With the pins 2 openings, it usually consumes 60 μA during empty load. This is a small one. cost.

Reduce the output noise

In the reference application, the existence of communication noise is reduced. One method is to reduce the bandwidth capacitor by increasing the size of the output. This is the only one that can be in 3 lead LP4950C, but the relative efficiency is low, because capacitors from 1 μF to 220 μF will only reduce the 100kHz bandwidth for 5V output, 430 μV to 160 μV RMS. By bypass electric containers can reduce noise by four times, because it reduces high -frequency gain from 4 to unit.

or about 0.01 μF. When performing this operation, the output capacitor must be increased to 3.3 μF to maintain stability. These changes reduce the output noise from 430 μV to 100kHz bandwidth when output of 100 μV RMS5V. In addition, the noise is no longer proportional to the output voltage, so under higher output voltage, improvement is more significant.