MAX9610 Maxim, MAX9610 Datasheet - Page 6

• Manufacturer Part Number: MAX9610
• Description: The MAX9610 high-side current-sense amplifier offers precision accuracy specifications of VOS less than 500µV (max) and gain error less than 0
• Manufacturer: Maxim

1µA, µDFN/SC70, Lithium-Ion Battery,
Precision Current-Sense Amplifier
The MAX9610 family of unidirectional high-side, cur-
rent-sense amplifiers features a 1.6V to 5.5V input com-
mon-mode range. The input range is excellent for
monitoring the current of a single-cell lithium-ion battery
(Li+), which at full charge is 4.2V, typically 3.6V in nor-
mal use, and less than 2.9V when ready to be
recharged. The MAX9610 is ideal for many battery-
powered, handheld devices because it uses only 1μA
quiescent supply current to extend battery life. The
MAX9610 monitors current through a current-sense
resistor and amplifies the voltage across that resistor.
See the Typical Operating Circuit on page 1.
The MAX9610 is a unidirectional current-sense amplifier
that has a well-established history. An op amp is used
to force the current through an internal gain resistor at
RS+ that has a value of R
equals the voltage drop across an external sense resis-
tor, R
same value as R
rent through R
is the same as its source current that flows through a
second gain resistor, R
voltage, V
R
of the two gain resistors R
Total gain = 25V/V for the MAX9610T, 50V/V for the
MAX9610F, and 100V/V for the MAX9610H.
Choose R
A high R
to drop due to IR loss. For minimal voltage loss, use the
lowest R
6
OUT
µDFN
2, 5
_______________________________________________________________________________________
1
3
4
6
SENSE
/R
PIN
1
SENSE
. The gain accuracy is based on the matching
SENSE
SENSE
OUT
SC70
. There is an internal resistor at RS- with the
1, 2
—
3
4
5
, whose magnitude is I
1
value.
value causes the power-source voltage
Applications Information
is sourced by a pFET. Its drain current
based on the following criteria.
1
Choosing the Sense Resistor
to minimize offset voltage. The cur-
NAME
GND
OUT
N.C.
RS+
RS-
Detailed Description
OUT
1
1
, such that its voltage drop
. This produces an output
Ground
No Connection. Not internally
connected.
Output
Load-Side Connection to
External Sense Resistor
Power-Side Connection to
External Sense Resistor
and R
Pin Description
OUT
FUNCTION
LOAD
(see Table 1).
Voltage Loss
x R
SENSE
x
The MAX9610 is unique since the supply voltage is the
input common-mode voltage (the average voltage at
RS+ and RS-). There is no separate V
input. Therefore, the OUT voltage swing is limited by
the minimum voltage at RS+.
and
V
minimum RS+ voltage. For best performance with a
3.6V supply voltage, select R
mately 120mV (gain of 25V/V), 60mV (gain of 50V/V), or
30mV (gain of 100V/V) of sense voltage for the full-
scale current in each application. These can be
increased by use of a higher minimum input voltage.
In the linear region (V
components to accuracy: input offset voltage (V
Gain Error (GE). The MAX9610 has V
and Gain Error of 0.5% (max). Use the following linear
equation to calculate total error.
A high R
sured more accurately because offsets are less signifi-
cant when the sense voltage is larger.
At high current levels, the I
significant. Take this into consideration when choosing
the resistor value and its power dissipation (wattage)
rating. Also, the sense resistor’s value might drift if it is
allowed to heat up excessively. The precision V
the MAX9610 allows the use of small sense resistors to
reduce power dissipation and reduce hot spots.
Table 1. MAX9610, Internal Gain Setting
Resistors (Typical Values)
SENSE
GAIN (V/V)
V
V
OUT(MAX)
OUT
full scale should be less than V
100
SENSE
50
25
= (Gain ± GE) x V
R
value allows lower currents to be mea-
SENSE
= V
RS+(MAX)
Efficiency and Power Dissipation
OUT Swing vs. V
OUT
R
=
100
200
400
1
G
(Ω)
×
< V
2
I
SENSE
SENSE
R loss in R
LOAD MAX
- V
V
OUT(MAX)
OUT
SENSE(MAX)
(
± (Gain x V
to provide approxi-
OS
CC
RS+
R
)
), there are two
OUT
OUT
= 500μV (max)
supply voltage
SENSE
10k
10k
10k
and V
/gain at the
(Ω)
- V
Accuracy
OS
OH
OS
can be
SENSE
)
OS
) and
of