MAX4208 Maxim, MAX4208 Datasheet - Page 15

• Manufacturer Part Number: MAX4208
• Description: The MAX4208/MAX4209 ultra-low offset and drift instrumentation amplifiers feature exceptional precision specifications, low power consumption, rail-to-rail output, excellent gain-bandwidth product, and buffered REFIN/MODE input in a very small &micro
• Manufacturer: Maxim

The ultra-low V
scale V
sive current sensing using milliohm sense resistors to
get high accuracy. Previous methods used the internal
resistance of the inductor in the step-down DC-DC con-
verter to measure the current, but the accuracy was
only 20% to 30%. Using a full-scale V
20µV max, V
Figure 5. MAX4208/MAX4209 Used as Precision Current-Sense Amplifiers for Notebook Computers with V
SENSE
Instrumentation Amplifiers with REF Buffer
of only 10mV to 20mV for minimally inva-
OS
OS
V
POWER IN R
OUT = G x 20mV = 100 x 20mV = 2V
SENSE
of the MAX4208/MAX4209 allows full-
error term is less than 0.1% and
______________________________________________________________________________________
= 10A x 0.002Ω = 20mV
SENSE
= 10A x 20mV = 200mW
1V AT 10A
V
DD
R4
R3
/2
G = 1 + R2
+V
0.002Ω
SENSE
SENSE
Ultra-Low Offset/Drift, Precision
R1
-
MAX4208
of 20mV, a
ASIC
MAX4209H
IN-
IN+
REFIN/MODE
REF
FB
MAX4209H gain error is 0.25% max at 100x, so the
total accuracy is greatly improved. The 0 to 2V output
of MAX4209H can be sent to an ADC for calculation.
The adjustable gain of MAX4208, can be set to a gain
of 250x using 1kΩ and 249kΩ resistors, to scale up a
lower 10mV V
age for wider dynamic range as needed.
IN+
IN-
REF
+3.3V
V
V
V
V
DD
SS
SS
DD
REFIN/MODE
OUT
Typical Application Circuit
SENSE
R2
FB
R1
REF
OUT
5V
ANTI-ALIASING
BUFFER OUT =
V
DD
FILTER
/2
C
voltage to a larger 2.5V output volt-
FB
ADC
SENSE
of 20mV
15