Detailed Description
Wideband Noise Reduction
To improve wideband noise and transient power-supply
noise, add a 0.1μF capacitor to NR (Figure 1). A 0.1μF NR
capacitor reduces the noise from 60nV/√Hz to 35nV/√Hz
for the 2.048V output. Noise in the power-supply input
can affect output noise, but can be reduced by adding an
optional bypass capacitor between IN and GND, as shown
in the Typical Operating Circuit. The 0.1Hz to 10Hz noise
when measured with a 0.1µF noise reduction capacitor (NR
pin) is 0.9μVP-P. Using a 100µF noise reduction capacitor
(NR pin) reduces the 0.1Hz to 10Hz noise to 0.6μVP-P.
Output Bypassing
The MAX6126 requires an output capacitor between
0.1μF and 10μF. Locate the output capacitor as close
to OUTF as possible. For applications driving switching
capacitive loads or rapidly changing load currents, it
is advantageous to use a 10μF capacitor in parallel
with a 0.1μF capacitor. Larger capacitor values reduce
transients on the reference output.
Supply Current
The quiescent supply current of the series-mode MAX6126
family is typically 380μA and is virtually independent of the
supply voltage, with only a 2μA/V (max) variation with
supply voltage.
When the supply voltage is below the minimum specified
input voltage during turn-on, the device can draw up to
300μA beyond the nominal supply current. The input voltage
source must be capable of providing this current to ensure
reliable turn-on.
Thermal Hysteresis
Thermal hysteresis is the change of output voltage at
TA = +25°C before and after the device is cycled over its
entire operating temperature range. The typical thermal
hysteresis value is 20ppm (SO package).
Turn-On Time
These devices typically turn on and settle to within 0.1%
of their final value in 200μs to 2ms depending on the
device. The turn-on time can increase up to 4ms with the
device operating at the minimum dropout voltage and
the maximum load. A noise reduction capacitor of 0.1μF
increases the turn-on time to 20ms.
Output Force and Sense
The MAX6126 provides independent connections for the
power-circuit output (OUTF) supplying current into a load,
and for the circuit input regulating the voltage applied
to that load (OUTS). This configuration allows for the
cancellation of the voltage drop on the lines connecting
the MAX6126 and the load. When using the Kelvin
connection made possible by the independent current
and voltage connections, take the power connection
to the load from OUTF, and bring a line from OUTS to
join the line from OUTF, at the point where the voltage
accuracy is needed. The MAX6126 has the same type
of Kelvin connection to cancel drops in the ground return
line. Connect the load to ground and bring a connection
from GNDS to exactly the same point.
Figure 1. Noise-Reduction Capacitor
PIN NAME FUNCTION
1 NR
Noise Reduction. Connect a 0.1µF
capacitor to improve wideband noise.
Leave unconnected if not used (see
Figure 1).
2 IN Positive Power-Supply Input
3 GND Ground
4 GNDS Ground-Sense Connection. Connect to
ground connection at load.
5, 8 I.C. Internally Connected. Do not connect
anything to these pins.
6 OUTS Voltage Reference Sense Output
7OUTF
Voltage Reference Force Output.
Short OUTF to OUTS as close to the
load as possible. Bypass OUTF with a
capacitor (0.1µF to 10µF) to GND.
NR
OUTF
*OPTIONAL.
0.1µF*
OUTS
REFERENCE
OUTPUT
(VOUT + 200mV) TO 12.6V INPUT
IN
GND GNDS
MAX6126
*
MAX6126 Ultra-High-Precision, Ultra-Low-Noise,
Series Voltage Reference
www.maximintegrated.com Maxim Integrated
│
16
Pin Description