LM4050AEM3-4.1T 데이터 시트보기 (PDF) - Maxim Integrated

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LM4050AEM3-4.1T

50ppm/°C Precision Micropower Shunt Voltage References with Multiple Reverse Breakdown Voltages

Maxim Integrated 

LM4050/LM4051

50ppm/°C Precision Micropower Shunt Voltage

References 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 LM4050/LM4051 shunt references use the bandgap

principle to produce a stable, accurate voltage. The device

behaves similarly to an ideal zener diode; a fixed voltage

is maintained across its output terminals when biased

with 60µA to 15mA of reverse current. The LM4050/

LM4051 clamps to a voltage of one diode drop below

ground when biased with forward currents up 10mA.

Figure 3 shows a typical operating circuit. The LM4050/

LM4051 are ideal for providing stable references from a

high-voltage power supply.

Applications Information

The LM4050/LM4051s’ internal pass transistors are used

to maintain a constant output voltage (VSHUNT) by sink-

ing the necessary amount of current across a source

resistor. The source resistance (RS) is determined from

the load current (ILOAD) range, supply voltage (VS) varia-

tions, 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

dissipation in the circuit by reducing the shunt current

(PD(TOTAL) = VS x 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 x (VS(MAX) - VSHUNT)

Output Capacitance

The LM4050/LM4051 do not require external capaci-

tors for frequency stability and are stable for any output

capacitance.

VS

ISHUNT + ILOAD

RS

ILOAD

VR

ISHUNT

LM4050

Figure 3. Typical Operating Circuit

Temperature Performance

The LM4050/LM4051 typically exhibit output voltage tem-

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

temperature coefficients may be different from one device

to another; some may have positive coefficients, and oth-

ers may have negative coefficients.

High Temperature Operation

The maximum junction temperature of the LM4050/

LM4051 is +150°C. The maximum operating temperature

for the LM4050/LM4051_E_ is +125°C. At a maximum

load current of 15mA and a maximum output voltage of

5V, the parts dissipate 75mW of power. The power dis-

sipation 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 parts self-heat to 35.56°C above ambient

temperature. If the ambient temperature is +125°C, the

parts operate at 159.56°C, thereby exceeding the maxi-

mum junction temperature value of +150°C. For high-

temperature operation, care must be taken to ensure the

combination of ambient temperature, output power dissi-

pation, 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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