Features

Stable, extensive output capacitor range

Working current: 45μA

Turn off current: 10 μA current limit can be adjusted

positive or negative negative Portal logic

Low -voltage linear voltage drop characteristics

Fixed 5V and adjustable versions

Allow reverse output voltage

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Simulation System

modem

Instrument

A/D and D/A Converter

Interface Driver

Battery power supply system

Instructions

lt #174; 1175 is a negative micro -power low -voltage difference regulator. Its static current is 45 μA and reduced to 10 μA when it was stopped. A new reference amplifier topological structure provides accurate DC characteristics and maintains a good loop stability output capacitor within a very wide range. Very low voltage drops and high efficiency are obtained through unique power transistor anti -saturation design. The adjustable 5V version is available. Some new functions make LT1175

very friendly. The SHDN pin can directly connect the positive or negative logic level. Users can choose currents at the following positions to limit 200 mAh, 400 mAh, 600 mAh and 800 mAh. The output can be forced to reverse the voltage without damage or atresia. Different from some early design, the current increased in the state of electricity is effectively restricted. LT1175 has a complete anti -spray protection function restriction, power restriction and heat shutdown. Special people noticed that the micro -power operating current operation of the high temperature problem prevent the output voltage increase during vacuum. LT1175 provides 8-needle PDIP and other packaging, 3-line SOT-223 and 5-needle surface installation DD and Tonghong To-220 packaging. 8 needle SO packing low thermal resistance structure.

Absolute maximum rated value

Input voltage (instant 1 second, Note 11) 25 volts

Input voltage (continuous) 20 volts 20 volts

Input and output deviation voltage (Note 12) 20 volts

5V induction pin (relative to GND pins) 2 volts, - 10 volts

Adjust the induction needle

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(About the output pins) 20 volts, — 0.5 volts

5V induction sales

(about the output pin) 20 volts, --7 volts

Output output Inverse voltage 2 voltage

SHDN pin to ground pins voltage (Note 2) 13.5 volts, --20 volts

SHDN pins to VIN pin voltage 30 volts, - 5 volts [ 123]

WorkersConcerned temperature range

LT1175C 0 ° C to 125 ° C

LT1175i – 40 ° C to 125 ° C

Environmental operating temperature range

LT1175C 0°C至70°C

LT1175I –40°C至85°C

储存温度范围–65°C至150°C

铅温度（焊接， 10 seconds) 300 degrees Celsius

Electric characteristics

indicates the scope suitable for working temperature

, otherwise the specifications are TA 25 ° C. VOUT 5V, VIN 7V, IOUT 0, VSHDN 3V, ILIM2 and ILIM4 are associated with vin, TJ 25 ° C, unless there is another explanation. In order to avoid the minimum and maximum confusion of negative voltage, all voltage is displayed as an absolute value, unless the polarity is not obvious.

Electric characteristics

indicates the scope of the working temperature

, otherwise the specifications are TA 25 ° C. VOUT 5V, VIN 7V, IOUT 0, VSHDN 3V, ILIM2 and ILIM4 are associated with vin, TJ 25 ° C, unless there is another explanation. In order to avoid the minimum and maximum confusion of negative voltage, all voltage is displayed as an absolute value, unless the polarity is not obvious.

Note 1: The absolute maximum rated value means that the value device that exceeds life may be damaged.

Note 2: The maximum positive voltage of the SHDN pin is 30V -VIN and grounded 13.5V. The maximum negative voltage is -20V for GND, -5V for -vin.

Note 3: 8 PMAX 1.5W, PMAX 6W packaged in 5. This power level is only applicable to input output voltage up to 12V and above internal power restrictions that may reduce power. See the limit curve of the typical performance characteristics of the current. Please note that the conditions must be met.

Note 4: Due to the power transistor base drive, the GND pins current increases. At the low input output voltage ( lt; 1V), when the power transistor is saturated, the GND pin current will be slightly higher. See typical performance characteristics.

Note 5: When ILOAD 0, when TJ GT; 125 ° C, the leakage of the power transistor may increase the output distribution or fixed 10 μA to 25 μA voltage induction pins, so that the output rises to the specified value above the specified value above the specified value. Essence Automatically pull up to prevent this situation from opening, but the power current will increase.

Note 6: This is the ground when the output voltage is pulled to the current within 1V.

Note 7: By setting the input voltage equal to normal adjustment output voltage and measurement voltage difference

vin and vout. For the current between 100mA and 500mA, the two ILIM pins are associated with the vehicle recognition number (VIN), and it can be based on VDO 0.15+1.1 (iOUT).

Note 8: Thermal regulation is the change temperature gradient of the output voltage caused by the mold, so it is proportional to the power consumption of the chip. The temperature gradient reaches the final value within 100ms. The voltage change after output 100ms is due to the changes in absolute mold temperature and reference voltage temperature coefficient.

Note 9: 0.8V's lower limit value guarantee will keep the regulator shut down. The upper limit of 2.5V ensures positive stabilizers. Any polarity can be used, refer to the GND pin.

Note 10: The measuring pulse width of load and line adjustment does not exceed 20ms on the basis of pulse to keep the chip temperature constant. DC regulation will be affected by the temperature of thermal regulation (Note 8) and the chip. When the load adjustment specification is also applicable to the current as the current as ILIM2 or ILIM4, the specified current limit is reached.

Note 11: When the input output voltage is higher than 12V, the current limit is reduced. For the guarantee limit, see the chart 12 or above in the typical performance characteristics.

Note 12: When running ( gt; 15V) load current is less than 5mA under a very large input and output deviation voltage, it is required to output capacitor ESR greater than 1 to prevent low -level output oscillation.

Typical performance features

Wave ripple suppression of the current independent independent independent of the current and the current between the input voltage and the load 25mA and 500mA Essence The larger the output capacitor, the more than 50 kilo. Under a very light load, I refused to use a larger output capacitor to improve

pins function

Sensor sales: induction volume for adjustable allowable customized selection of the output voltage of the output voltage A version of the outer frequency device is set to generate a 3.8V voltage at the detection pin. Under normal circumstances, the current of the input end is 75NA. The maximum compulsory voltage on the induction pin is 2V and -10V about GND pins. The fixed 5V version uses the sensor foot to realize the transistor with higher the load or drive the external channel output current. The bias current outputs 5V sensing pin is about 12 μA. Separational induction and output pins also allow compensation technology information departments described in a new circuit application.

SHDN PIN: SHDN PIN is specially configured to allow positive voltage logic or only negative logic. Forced SHDN pin 2V or lower or lower than the GND pin will open the regulator. This makes the positive logic signal actively stop. likeIf there is no positive voltage, the SHDN pin can be driven to the GND pins to turn on the regulator. When keeping it open, the SHDN pin will default to the opening state by default. All the voltage is lower than the absolute maximum rated value, and the SHDN pin only draws a few Weian current (see typical performance characteristics). The maximum voltage on the SHDN pin is 15V, for the GND pin to -20V, the GND pin is 35V, the --5V is relative to the negative input pin

Ilim pin: the two current limit pins are the pin. Launch the pole part of the power transistor. When keeping it open, they will float a few 100 millivolo higher than the negative input voltage. For short circuits input voltage, the current limitation increases ILIM2 at least 200mA, and ILIM4 is at least 400mA. These pins must only be connected to the input voltage, or directly or through the resistance.

Output pin: The output pin is the power transistor of NPN. It can force input voltage ground or up to 2V positive damage or atresses (see output voltage reversal of the application information part). LT1175 has a folding function current limit, so the maximum current of the output pins is the input output voltage function. See typical performance characteristics.

GND pin: The static current of the GND pins is 45 μA zero load current, and the output current MA is increased for each increase. When the output current is 500mA, the GND pin current is about 5mA. The current flows into GND pins.

Set output voltage

The adjustable version of the LT1175 has a feedback sensing voltage of 3.8V, and the bias current is about 75NA from the induction needle. Avoid errors caused by the current of the output voltage. Table 1 shows the recommended resistance value in the output voltage range. The second part of the table shows the resistance value of only 10 μA. The output voltage error is about 0.4%and the highest value of the bias current of low -value resistance, and the maximum value is about 1%. The article also gives the formula for calculating resistance for any output voltage

LT1175-5 is a fixed 5V design with sensory pins as an output Kelvin connection. Usually, the inductive pipe foot and the output tube foot are directly connected together, or it is close to the regulator or at the remote load point.

current setting limit

LT1175 uses two ILIM pins to set current limit (typical) 200 mAh, 400 mAh, 600 mAh or 600 mAh or 800 mAh. The corresponding minimum guarantee current is 130mA, 260mA, 390MA520 mAh. This allows users to choose the current restrictions based on specific applications to prevent short -circuit current ratio to full load current. Excessive power loss in the input power overload or failure load has been excluded. The power limit in the form of folding current limit has built -in and reduces the current limit as a lossThe function of the output voltage difference is used to exceed 14V. See the typical performance characteristic diagram. In any case, the LT1175 guarantees anti -spraying restrictions. Power limit and heat shutdown protection equipment is exempted from damaging the knot temperature under all load conditions.

Turn off

When the shutdown, LT1175 consumes about 10 μA. Special circuits are used to maximize the increase of the current at high temperature parking, but it can be seen that slightly increased higher than 125 ° C. One option that was not taken was the output shutdown when the initiative was turned off. This means that after starting the stop, the output will decrease at a slowly rate and determine the load current plus 12 μA internal load, and the size of the output capacitor. Active drop -down is a good thing that is usually used alone, but it prevents users from turning off the regulator when the second power supply is connected to the LT1175 output. If you need to actively output off when you stop, it can use the exhaustive mode PFET as the external addition as shown in Figure 2. Note that the maximum holding PFET voltage must be lower than the positive logic high level to ensure that the device is activated in the regulator. Motorola J177 equipment has a grid pole voltage to zero, and the pitch resistance is 300

The minimum drop voltage

The drop voltage refers to the input and output of the proper output adjustment. For the older 3 -terminal stabilizer, the voltage drop is usually 1.5V to 3V. The LT1175 uses saturated power transistor design, which greatly reduces the voltage drop. Usually it is 100 millivolochia at the time of light load and 450 millivolves at full load. Special preventive measures are taken to ensure that the technology does not cause the static power supply current to be too high under light load conditions. When the voltage is too low when the regulator is input, a adjustable output cannot be maintained, and the rules and regulations are maintained by the error amplifier of the error amplifier through the transistor. The current transistor consumed by the driver can be dozens of milliamps, and even uses very little or output without load. The situation of the elderly is indeed so saturated when the power transistor is saturated. LT1175 uses new anti -saturation technology to prevent high -drive current, however, this makes the power transistor close to its theoretical value saturation limit.

Output capacitor

uses several new regulator design technology LT1175 for the choice of output capacitors. Just like most of the low -drop school design of the collector or the drain of the power transistor to drive output nodes, the LT1175 uses the output capacitor as the overall loop compensation. The minimum value of the older regulatory agencies is 1 μF to 100 μF, and the maximum ESR (effective series resistance) is 0.1 to 1 , the minimum ESR is 0.03 to 0.03 0.3 . These restrictions can usually only be in high -quality solids. Aluminum capacitors have the problem of high ESR, unless the capacitance value (physical). The voltage of ESR ceramic or film capacitors is too low,This makes the zero frequency of the capacitance/ESR too high and cannot maintain the phase margin in the regulator. In the previous design, even if there is the best capacitor, the loop phase is also very low when the output current is low. These problems have led to a new LT1175 error amplifier and internal frequency compensation design technology, as shown in Figure 3.

The traditional regulatory circuit error amplifier forms A1, drives the transistor Q2 and the power transistor Q1. The basic cycle is added to the error amplifier from Q3 and DC feedback current feedback. This is not a problem because there is almost no gain under light load. In addition to low -gain, the parasitic variance base of Q2 is expanded from DC feedback. Combining these two effects significantly improved the difference in the loading load, so that the ring road has tolerance to the large ESR in the output capacitor. The heavy load, the load phase and the income are almost not so troublesome and huge negative growth feedback to reduce the adjustment. Q1 Basic emission pole voltage characteristics make Q3 negative reduced feedback under heavy load to prevent poor adjustment. In traditional design, even if non -linear feedback is used, ESR with medium to output capacitors is lower than

0.3 This situation may occur in a capacitor with ESR on ceramics or thin films more than 0.1 . In the previous design, the user was forced to add a real resistance to connect with the capacitor to ensure the stability of the circuit. This LT1175 uses a unique communication technology to solve this problem. CF is a traditional feed capacitor, which is often used in the regulator to offset the polarity formed through the output capacitor. It is usually the internal node display from the adjustment output node to the feedback node R1/R2 or on the feedback node. However, in this case, the capacitor is the internal structure of the connected power transistor. RC is an inevitable parasitic hosted by the power supply. The node accessing the bottom of the RC is only available in a single -chip structure. In this structure, Kelvin can be connected to the NPN buried collector layer.

The current response of the cycle is like RC and output capacitors and good circuit stability, and even the ESR of the output capacitor is extremely low. The end result of all these concerns of the stability of the circuit is that the output capacitors used by the LT1175 can be used from 0.1 μF to hundreds of microla, and ESR uses ESR from 0 to 10 This range allows the use of ceramics, solids, aluminum, and film capacitors. The best output capacitor type of LT1175 is still there is still a considerable solid. If a large load current is expected to require a larger capacitor with a lower ESR to control the output change in the worst case during the transient period. If the transient is not a problem, the capacitor can choose small volume, low price, etc., worrying that the current price of the price of the electric container is to the output capacitor, because the LT1175 limitThe flowing current is far lower than the level that may cause damage to the capacitor. The surge caused by the short -circuit regulator output is not a problem, because the electric container will not fail during the period of shorting , only during the charging period. The output capacitor should be in the inch of several regulators. If the remote sensing is used, the output capacitor can be set on the remote control node, but the GND pin of the regulator should also be connected to the remote site. The basic principle is to maintain a rational GND pin near the output capacitor, no matter where it is. When a very large input and output voltage difference ( gt; 5V), the load current is less than 5mA, the output capacitor of ESR is greater than 1 low -level output oscillation.

Input capacitors

LT1175 requires a separate input bypass container. Only when the regulator is located at the original power output capacitor. 1 μF or larger 在 It is recommended to use a capacitor in all applications, but if ESR has a lower output using capacitors such as ceramics or film and input capacitors, the input capacitor should at least output the capacitor value. If the input capacitor is used when it is used for solid ravioli or aluminum electrolytic output capacitors.

High temperature operation

LT1175 is a micro -power design with only 45 μA static current. This may make it at high temperature ( gt; 125 ° C), and the leakage of power transistors may exceed the output node load current (5 μA to 15 μA). To avoid high -temperature air loads when the output voltage drifting is not controlled in this case, the LT1175 has a motivated load starting when the output is pulled to the rated value. This load absorbs the leakage of the transistor and maintains good supervision. There is a disadvantage, but the function. If the output is deliberately increased, the output of the LT1175 as a first -class regulator LT1175 will be slightly higher as a load that is not needed on the first -class regulator. Because of this, active pulling is intentionally weak . It can model a 2K resistor and an output of a regulator to output high clamp voltage when being pulled by a regulator. For example, if a 4.8V output is pulled to 5V, the voltage on the load main regulator is (5V – 4.8V)/2K 100 μA. This also means that if the endless transistor leaks 50 μA, the output voltage is (50 μA) (2K ) 100MV high. Under normal circumstances, this situation does not occur, but the short circuit may overheat the chip in the short circuit.

Thermal factors

LT1175 provides a special 8 -pin surface installation with packaging paddles connecting to mold accessories. When the pins 1 and 8 are connected to the PC extension copper plate. Table 2 shows a combination of various copper land and back or internal aircraft. Table 2 also shows the heat resistance DD surface packaging and 8 -pin immersion packaging of 5 stitches

Calculating mold temperature, maximum power consumption or maximum input voltage, use the following using the following The formula is based on the correct heat in Table 2Resistance. To-220 is used to use θja 50 ° C/W without a radiator and θja 5 ° C/W+heat sink to use the resistance of the radiator.

TA the highest ambient temperature

tmax maximum LT1175 mold temperature (125 ° C commercial and industrial level)

θja LT11755555555 Thermal resistance, connected to the environment

vin Maximum continuous input voltage

Load current

ILOAD Maximum load current

Example: LT1175S8, ILOAD 200MA , VOUT 5V, VIN 7V, TA 60 ° C. The maximum mold temperature LT1175S8 is 125 ° C. The thermal resistance in Table 2 is

The result is 80 ° C/W. Mold temperature 60+80 (0.2A) (8–5) 108 ° C

The output voltage reversal

LT1175 Design is designed to bear the output The voltage reversal is as high as 2V. For example, if the output is short -circuited to the positive 5 volt power. This is almost certain that destroying IC device output that is connected to the negative electrode. If the positive power supply is first connected, the load is connected between the positive and negative power. For these reasons, adding a negative design practice from each regulator output to grounding bias diode restriction output voltage reversal. The rated value of the diode should be processed by the full -negative load current under startup, or if the power supply is short -circuited to the power supply, the short -circuit current of the positive pole power must be allowed. The input voltage is lower than the positive low -voltage differential regulator LT1121 and LT1129 of the output voltage linear technology. If the input voltage is less than the output voltage. These devices use the horizontal PNP power transistor structure with 40V transmitted pole. However, the LT1175 uses the NPN power transistor structure with parasitic diode between the input and output of the regulator. The voltage between the reverse input and the output exceeds 1V to damage the regulator, if the large current flows. Simply put, when the output remains unchanged, the input source will not cause damage even if the input is slightly upside down. Power supply generates a regulator that does not adjust or adjusts the input voltage. The voltage will contain high -frequency ripples and must be suppressed by a linear regulator. Pay special attention to the maximum RT1175 to maximize the frequency ripple suppression, but in any micro -power design, the inhibitory rate is strongly affected by the ripple frequency. Typical performance characteristics Figure section shows 60DB suppression at 1kHz, but only 15DB5V is suppressed at 100kHz. Digital photos 4A and 4B display the actual output lines wave formula and three -wave input ripples.

Application information

In order to estimate the regulator output ripple under different conditions, the following general opinions should be helpful:

Affected by weakness is determined by load current or output capacitor size. Under a very light load ( lt; 10mA), using larger output can reduce higher frequency ripple capacitors.

2. The feed capacitor with the resistance of the resistor split device is used with the adjustable part, which can effectively reduce the ripple that the output voltage of the lines greater than 5V is less than 100kHz.

3. Input the output voltage difference pair

Circuit ripple suppression until the regulator actually enters the voltage drop condition of 0.2V to 0.6V. If you need to improve the ripple suppression, the input filter can be added. This filter can be a simple RC filter with 1 resistance to 10 resistors. For example, 3.3 resistor, combined with 0.3 ESR solid 钽 capacitors, which will produce additional 20DB ripple suppression. The size of the resistor is determined by the maximum load current. If the voltage allowed on the maximum resistor is reduced to VR , and the maximum load current is ILOAD, R VR/ILOAD. Under light, you can use loads, large resistors and smaller capacitors to save space. Under heavier loads, inductors may be used to replace the resistor. The value of the sensor can calculate the formula:

ESR effective series resistance of the filter capacitor. Compared with ESR, this assumption is a reasonable hypothesis of 2.2 μF and a solid cavator with a 2.2 μF and 50kHz or more.

f ripple frequency

rr ripple suppression ratio of the filter, unit: db

Example: ESR 1.2 F 100kHz, F 100kHz, rr –25db

It is recommended that the filter uses a solid cavior to keep the filter Q is quite low. This can prevent the oscillation of the resonance frequency of the filter and the combination of the filter/regulator combination.