Datasheet

MAX6070/MAX6071
Low-Noise, High-Precision Series
Voltage References
20Maxim Integrated
Detailed Description
Wideband Noise Reduction (FILTER)
To improve wideband noise and transient power-supply
noise with the MAX6070, connect a 0.1FF capacitor from
FILTER to GND (see the Typical Operating Characteristics).
Larger values do not appreciably improve noise reduction.
A 0.1FF capacitor reduces the spectral noise density at
1kHz from 60nV/√Hz to 30nV/√Hz for the 2.5V output.
Noise at the input pin can affect output noise, but can
be reduced by connecting an optional bypass capacitor
between IN and GND as shown in Figure 1.
Output Bypassing
The MAX6070/MAX6071 require an output capacitor
between 0.1FF and 10FF. Place the output capacitor
as close to OUTF as possible. For applications driving
switching capacitive loads or rapidly changing load cur-
rents, use a 0.1µF capacitor in parallel with a larger load
capacitor to reduce equivalent series resistance (ESR).
Larger capacitor values and lower ESR reduce transients
on the reference output.
Supply Current
The MAX6070/MAX6071 draw 150FA of current and are
virtually independent of the supply voltage, with only a
1.6FA/V variation with supply voltage.
Thermal Hysteresis
Thermal hysteresis is the change of output voltage at
T
A
= +25NC before and after the device is cycled over its
entire operating temperature range. The typical thermal
hysteresis value is 85ppm.
Turn-On Time
These devices typically turn on and settle to within 0.01%
of their final value in 30Fs. A noise reduction capacitor of
0.1FF increases the turn-on time of the MAX6070 to 10ms.
Output Force and Sense
The MAX6070/MAX6071 provide independent connec-
tions for the force output (OUTF) supplying current to the
load and the circuit input regulating the load voltage via
the output sense pin (OUTS). This configuration allows for
the cancellation of the voltage drop on the lines connect-
ing the MAX6070/MAX6071 and the load. When using
the Kelvin connection made possible by the independent
force and sense outputs, connect OUTF to the load and
connect OUTS to OUTF at the point where the voltage
accuracy is needed (see Figure 1). The MAX6071 fea-
tures the same type of Kelvin connection to cancel drops
in the ground return line. Connect the load to ground and
connect GNDS to ground as close as possible to the load
ground connection (see Figure 2).
Shutdown
The MAX6070/MAX6071 feature an active-high enable
pin (EN). Pulling EN low disables the output with a resis-
tive load to ground and forces the quiescent current to
less than 1µA. The value of the load is typically 200kω.
Pulling EN high enables normal operation.
Applications Information
Wideband Noise Reduction
Figure 1
shows a typical noise reduction filter application
circuit. Note that the use of the wideband noise filter will
increase turn-on time.
High-Resolution DAC and
Reference from a Single Supply
Figure 2
shows a typical circuit providing the reference
for a high-resolution, 16-bit MAX541 DAC.
Precision Current Source
Figure 3
shows a typical circuit providing a precision cur-
rent source. The OUTF output provides the bias current
for the bipolar transistor. OUTS and GNDS sense the volt-
age across the resistor and adjust the current sourced by
OUTF accordingly.
Figure 1. Reference Output Kelvin Connection
FILTER
GND
EN
OUTF
OUTS
IN
5V SUPPLY
LOAD
MAX60700.1µF
0.1µF
0.1µF