LM4040AIX3-3.0T 查看數據表（PDF） - Maxim Integrated

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LM4040AIX3-3.0T

Improved Precision Micropower Shunt Voltage Reference with Multiple Reverse Breakdown Voltages

Maxim Integrated 

Improved Precision Micropower Shunt Voltage

Reference with Multiple Reverse Breakdown Voltages

Pin Description

PIN

NAME

FUNCTION

1

+

Positive Terminal of the Shunt Reference

2

−

Negative Terminal of the Shunt Reference

3

N.C. No connection. Leave this pin unconnected or connected to pin 2.

Detailed Description

The LM4040 shunt references use the bandgap princi-

ple to produce a stable, accurate voltage. The device

behaves similarly to an ideal zener diode; a fixed volt-

age is maintained across its output terminals when

biased with 60µA to 15mA of reverse current. The

LM4040 behaves similarly to a silicon diode when

biased with forward currents up 10mA.

Figure 3 shows a typical operating circuit. The LM4040

is ideal for providing a stable reference from a high-

voltage power supply.

Applications Information

The LM4040’s internal pass transistor is used to maintain a

constant output voltage (VSHUNT) by sinking the necessary

amount of current across a source resistor. The source

resistance (RS) is determined from the load current (ILOAD)

range, supply voltage (VS) variations, VSHUNT, and desired

quiescent current.

Choose the value of RS when VS is at a minimum and ILOAD

is at a maximum. Maintain a minimum ISHUNT of 60µA at all

times. The RS value should be large enough to keep

ISHUNT less than 15mA for proper regulation when VS is

maximum and ILOAD is at a minimum. To prevent damage

to the device, ISHUNT should never exceed 20mA.

Therefore, the value of RS is bounded by the following

equation:

[VS(MIN) - VR ] / [60µA + ILOAD(MAX)] > RS >

[VS(MAX) - VR ] / [20mA + ILOAD(MIN)]

Choosing a larger resistance minimizes the total power dis-

sipation in the circuit by reducing the shunt current

(PD(TOTAL) = VS  ISHUNT). Provide a safety margin to

incorporate the worst-case tolerance of the resistor used.

Ensure that the resistor’s power rating is adequate, using

the following general power equation:

PDR = ISHUNT  (VS(MAX) - VSHUNT)

Output Capacitance

The LM4040 does not require an external capacitor for fre-

quency stability and is stable for any output capacitance.

VS

ISHUNT + ILOAD

RS

ILOAD

VR

ISHUNT

LM4040

Figure 3. Typical Operating Circuit

Temperature Performance

The LM4040 typically exhibits an output voltage tem-

perature coefficient within ±15ppm/°C. The polarity of

the temperature coefficient may be different from one

device to another; some may have positive coefficients,

and others may have negative coefficients.

High Temperature Operation

The maximum junction temperature of the LM4040 is

+150°C. The maximum operating temperature for the

LM4040_E_ is +125°C. At a maximum load current of 15mA

and a maximum output voltage of 5V, the part will dissipate

75mW of power. The power dissipation limits of the 3-pin

SC70 call for a derating value of 2.17mW/°C above +70°C

and thus for 75mW of power dissipation, the part will self-

heat to 35.56°C above ambient temperature. If the ambient

temperature is +125°C, the part operates at 159.56°C,

thereby exceeding the maximum junction temperature

value of +150°C. For high-temperature operation, care must

be taken to ensure the combination of ambient temperature,

output power dissipation and package thermal resistance

does not conspire to raise the device temperature beyond

that listed in the Absolute Maximum Ratings. Either reduce

the output load current or the ambient temperature to keep

the part within the limits.

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