MAX4072 Maxim, MAX4072 Datasheet - Page 11

• Manufacturer Part Number: MAX4072
• Description: The MAX4069–MAX4072 low-cost, bidirectional, high-side, current-sense amplifiers are ideal for monitoring battery charge and discharge currents in notebooks, cell phones, and other portable equipment
• Manufacturer: Maxim

Figure 2. Bidirectional Current Monitor
The MAX4072 contains REFIN pin for external refer-
ence voltage. The allowable voltage range on REFIN is
1V (min) to 4V (max) with V
The REFOUT of the MAX4069/MAX4070/MAX4071 can
sink 100µA and source 500µA. Keep the total capaci-
tance on REFOUT under 500pF to maintain stability.
Ideally, the maximum load current develops the full-
scale sense voltage across the current-sense resistor.
Choose the gain needed to yield the maximum output
voltage required for the application:
where V
gain of 50V/V, or 50mV for gain of 100V/V. A
gain of the device.
In applications monitoring high current, ensure that
R
tor’s power dissipation is exceeded, its value may drift
or it may fail altogether, causing a differential voltage
across the terminals in excess of the absolute maxi-
mum ratings. Use resistors specified for current- sens-
ing applications.
SENSE
SENSE
is able to dissipate its own I
Recommended Component Values
CELLS
2
is the full-scale sense voltage, 75mV for
External Reference (MAX4072)
(MAX4069/MAX4060/MAX4071)
V
______________________________________________________________________________________
OUT
I
DISCHARGE
Bidirectional, High-Side, Current-Sense
= V
CC
SENSE
≥ 5.1V.
V
GSEL
SHDN
CC
Reference Output
RS-
x A
2
MAX4070
R
V
R loss. If the resis-
SENSE
GND
RS+
REFOUT
I
CHARGE
OUT
V
is the
TO ADC
2.5V
Amplifiers with Reference
LOAD
The MAX4069–MAX4072 sense a wide variety of cur-
rents with different sense-resistor values. Table 1 lists
common resistor values for typical operation of these
devices. Listed output voltage is with respect to REF.
Choose R
Voltage Loss: A high R
source voltage to degrade through IR loss. For minimal
voltage loss, use the lowest R
Accuracy: A high R
to be measured more accurately. This is because off-
sets become less significant when the sense voltage is
larger. For best performance, select R
approximately 75mV (gain of 50V/V) or 50mV (gain of
100V/V) of sense voltage for the full-scale current in
each application.
Efficiency and Power Dissipation: At high-current lev-
els, the I
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.
Inductance: Keep inductance low if I
high-frequency component. Wire-wound resistors have
the highest inductance, while metal film is somewhat
better. Low-inductance metal-film resistors are also
available. Instead of being spiral-wrapped round a
-25mV
V
DISCHARGE
CURRENT
OUT
2
SENSE
R losses in R
- V
REF
0
based on the following criteria:
5V
2.5V
-2.5V
SENSE
SENSE
SENSE
Sense Resistor, R
25mV
value allows lower currents
SENSE
A
V
value causes the power-
can be significant. Take
= 100
V
SENSE
value.
CURRENT
CHARGE
SENSE
SENSE
50mV
has a large
to provide
SENSE
11