MAX874

10µA, Low-Dropout,

Precision Voltage References

________________________________________________________________Maxim Integrated Products 1

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General Description

The MAX872/MAX874 precision 2.5V and 4.096V micro-power voltage references consume a maximum of only 10µA and operate from supply voltages up to 20V. The combination of ultra-low quiescent current and low 200mV dropout makes them ideal for battery-powered equipment. They source and sink up to 500µA with only 200mV input voltage headroom, which makes the 2.5V MAX872 ideal for use with a 3V supply and the 4.096V MAX874 ideal for use with a 5V supply.

Initial accuracy of 0.2% at +25°C (±5mV for the MAX872,±8mV for the MAX874) and low 40ppm/°C max drift make these references suitable for a wide range of precision applications.

Applications

Hand-Held Instruments Battery-Operated Equipment Power Supplies

Features

o Output Voltage

2.500V ±0.2% (MAX872)4.096V ±0.2% (MAX874)o Wide Operating Voltage Range

2.7V to 20V (MAX872)4.3V to 20V (MAX874)o 10µA Max Supply Current

o 40ppm/°C Max Drift Over Extended Temp. Range o Line Regulation Over Temp.

20µV/V (MAX872)75µV/V (MAX874)o Load Regulation Over Temp.

0.6mV/mA Max (MAX872)1.0mV/mA Max (MAX874)

o ±500µA Sink/Source Current

Typical Operating Circuit

19-0005; Rev 2; 6/97

*Dice are specified at +25°C only.

Pin Configuration

Ordering Information

M A X 872/M A X 874

10µA, Low-Dropout,

Precision Voltage References 2_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS—MAX872

(V IN = 2.7V, I L = 0mA, T A = +25°C, unless otherwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage.......................................................................24V Output Short-Circuit Duration..........Continuous to Either Supply C COMP Input...........................................................-0.3V to V OUT TRIM Input...................................................-0.3V to (V IN + 0.3V)TEMP Output ...............................................-0.3V to (V IN + 0.3V)Continuous Power Dissipation (T A = +70°C)

Plastic DIP (derate 9.09mW/°C above +70°C).............727mW SO (derate 5.88mW/°C above +70°C)..........................471mW

Operating Temperature Ranges

MAX87_C__.........................................................0°C to +70°C MAX87_E__......................................................-40°C to +85°C Storage Temperature Range.............................-65°C to +150°C Junction Temperature Range (T j )......................-65°C to +160°C Lead Temperature (soldering, 10sec).............................+300°C

ELECTRICAL CHARACTERISTICS—MAX874

(V IN = 4.3V, I L = 0mA, T A = +25°C, unless otherwise noted.)

MAX872/MAX874

10µA, Low-Dropout,

Precision Voltage References

_______________________________________________________________________________________3

Note 1:If the load current exceeds 300µA, connect a minimum of 1000pF from V OUT to GND. Note that if a capacitor larger than

1000pF is used, a compensation capacitor of C OUT /100 must be connected from V OUT to COMP.

ELECTRICAL CHARACTERISTICS—MAX872C

(V IN = 2.7V, I L = 0mA, T A = 0°C to +70°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS—MAX874C

(V

IN = 4.3V, I L = 0mA, T A = 0°C to +70°C, unless otherwise noted.)

M A X 872/M A X 874

10µA, Low-Dropout,

Precision Voltage References 4_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS—MAX872E

(V IN = 2.7V, I L = 0mA, T A = -40°C to +85°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS—MAX874E

(V IN = 4.3V, I L = 0mA, T A = -40°C to +85°C, unless otherwise noted.)

MAX872/MAX874

10µA, Low-Dropout,

Precision Voltage References

_______________________________________________________________________________________5

50

150

100

200

250100

150

200

250

DROPOUT VOLTAGE vs. SOURCE CURRENT

SOURCE CURRENT (µA)

D R O P O U T V O L T A G

E (m V )

10

5

15

200

2

4

6

8

101214161820

SUPPLY CURRENT vs. INPUT VOLTAGE

INPUT VOLTAGE (V)

S U P P L Y C U R R E N T (µA )

510

15

20

-50

-25

25

50

75

100

MAX872

SUPPLY CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

S U P P L Y C U R R E N T (µA )

515

1020

25-50

-25

25

50

75

100

MAX874

SUPPLY CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

S U P P L Y C U R R E N T (µA )

02

1

3

4-50

-25

25

50

75

100

MAX872

LOAD REGULATION vs. TEMPERATURE

TEMPERATURE (°C)

L O A D R E G U L A T I O N (m V /m A )

2.495

2.498

2.500

2.503

2.5052

6

10

16

4

8

14

18

12

20

MAX872

OUTPUT VOLTAGE vs. INPUT VOLTAGE

M A X 872/74-05

INPUT VOLTAGE (V)

V O U T (V )

4.090

4.094

4.092

4.09.098

4.100

4

8

12

16

6

10

14

18

20

MAX874

OUTPUT VOLTAGE vs. INPUT VOLTAGE

M A X 872/74-06

INPUT VOLTAGE (V)

V O U T (V

)

03

2

1

4

5-50

-25

25

50

75

100

MAX874

LOAD REGULATION vs. TEMPERATURE

TEMPERATURE (°C)

L O A D R E G U L A T I O N (m V /m A )

2.498

0.01

10

1

0.1

MAX872OUTPUT VOLTAGE vs. SOURCE CURRENT

2.5012.500

2.502

2.499

M A X 872/74-09

SOURCE CURRENT (mA)

V O U T (V )

Typical Operating Characteristics

(V IN = 3V (MAX872), V IN = 5V (MAX874), no load, T A = +25°C, unless otherwise noted.)

M A X 872/M A X 874

10µA, Low-Dropout,

Precision Voltage References 6_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V IN = 3V (MAX872), V IN = 5V (MAX874), no load, T A = +25°C, unless otherwise noted.)

4.094

0.01

10

1

0.1

MAX874OUTPUT VOLTAGE vs. SOURCE CURRENT

4.0974.096

4.098

4.095

M A X 872/74-10

SOURCE CURRENT (mA)

V O U T (V )

2.496

2.498

2.502

2.500

2.504

2.506

-50

-25

25

50

75

100

MAX872

OUTPUT VOLTAGE vs. TEMPERATURE

M A X 872/74-11

TEMPERATURE (°C)

V O U T (V )

4.090

4.092

4.096

4.094

4.098

4.100

-50

-25

25

50

75

100

MAX874

OUTPUT VOLTAGE vs. TEMPERATURE

M A X 872/74-12

TEMPERATURE (°C)

V O U T (V )

-20

-80

1

1001k

10

10k

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

-60

FREQUENCY (Hz)

P S R R (d B )

-40

MAX872

1Hz TO 100Hz NOISE 0.5

0.6

0.8

0.7

0.91.0

-50

-25

25

50

75

100

TEMP OUTPUT vs. TEMPERATURE

TEMPERATURE (°C)

T E M P O U T P U T (V )

2.0

1

1001k

10

10k

NOISE vs. FREQUENCY

0.5

FREQUENCY (Hz)

N O I S E (m V p -p )

1.51.0

MAX874

1Hz TO 100Hz NOISE

Applications Information

Trimming the Output Voltage

The MAX872/MAX874’s output voltage is trimmed for 0.2% tolerance at +25°C. If additional V OUT trimming is desired, connect a potentiometer to TRIM, as shown in Figures 1a and 1b. Adjusting V OUT away from its facto-ry-trimmed voltage typically changes the output voltage tempco by 7ppm/°C per 100mV.

Reducing Input Ripple with an Input Filter

The Power-Supply Rejection Ratio vs. Frequency graph in the Typical Operating Characteristics shows ripple rejection between 10Hz and 2kHz. As input RC filter with a pole less than 10Hz, as shown in Figure 2, fur-ther attenuates input ripple with this band. The voltage drop across the input resistor (due to supply and load current) slightly increases the dropout voltage. The increase is given by [(I LOAD + I SUPPLY ) • R].

Choosing the Output and Compensation Capacitors

Connecting a capacitor between Void and GND reduces load transients. If the load exceeds 300µA,connect a minimum of 1000pF from V OUT to GND. The type of capacitor is not critical. If the total load capaci-tance from V OUT to GND (C LOAD = output capacitor +other capacitive load) is larger than 1000pF, connect a compensation capacitor with a value of C LOAD /100between COMP and V OUT .

MAX872/MAX874

10µA, Low-Dropout,

Precision Voltage References

_______________________________________________________________________________________7

Pin Description

Internal Connection. Make no connection to this pin I.C.1, 7PIN FUNCTION

NAME Input Voltage

V IN 2Ground

GND

4

Temperature-Proportional Output Voltage. Generates an output voltage proportional to junction temperature.TEMP 3Output Voltage Trim. Connect to the center of a voltage divider for output trimming. Otherwise make no connection.TRIM

5Compensation Input. Connect

C LOA

D /100 capacitor from V OUT to COMP to provide capacitive load compensation.

COMP

8Reference Output

V OUT

6

Figure 1a. Adjusting V OUT with the TRIM Input on the MAX872

Figure 1b. Adjusting V OUT with the TRIM Input on the MAX874

M A X 872/M A X 874

10µA, Low-Dropout,

Precision Voltage References Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600©1997 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

TEMP Output

The TEMP output provides a voltage proportional to the MAX872/MAX874 junction temperature. Since the power dissipation of the MAX872/MAX874 is <100µW typ, the junction temperature is within 0.5°C of the ambient temperature. Although it goes unused in most applications, the ambient temperature information given by the TEMP output may be used to control LCD contrast, or to provide ADC gain compensation or ther-mal out-of-range indication. TEMP must be buffered or connected to a high-impedance input.

Operating Temperature

Window Comparator

In Figure 3, a window comparator monitors the TEMP output and indicates if the temperature is out of the nominal operating range. For the resistor values shown,the circuit will indicate an out-of-range condition if the ambient temperature should rise above +85°C or dip below -40°C.

Start-Up

When the input voltage is below the factory-selected output voltage, the MAX872/MAX874 can draw exces-sive supply current (hundreds of microamps). If the source resistance is too high, the voltage drop across the source resistance can prevent the input voltage to the device from reaching the minimum dropout voltage.Therefore, when using the MAX872/MAX874 in low-dropout applications, ensure that the power supply has a low source resistance.

Figure 2. Input Filter Reduces Input Ripple

Figure 3. Operating Temperature Range Window Comparator

___________________Chip Topography

GND

TEMP

V IN *N.C.OUT

TRIM

0.110"(2.794mm)

0.072"(1.829mm)

*N.C.COMP

*MAKE NO CONNECTIONS TO THESE PADS

TRANSISTOR COUNT:

SUBSTRATE CONNECTED TO GND.

MAX872/MAX874