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PDF MAX472 Data sheet ( Hoja de datos )
| Número de pieza | MAX472 | |
| Descripción | Precision / High-Side Current-Sense Amplifiers | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-0335; Rev 2; 12/96
Precision, High-Side
Current-Sense Amplifiers
_______________General Description
The MAX471/MAX472 are complete, bidirectional, high-
side current-sense amplifiers for portable PCs, tele-
phones, and other systems where battery/DC
power-line monitoring is critical. High-side power-line
monitoring is especially useful in battery-powered sys-
tems, since it does not interfere with the ground paths
of the battery chargers or monitors often found in
“smart” batteries.
The MAX471 has an internal 35mΩ current-sense resis-
tor and measures battery currents up to ±3A. For appli-
cations requiring higher current or increased flexibility,
the MAX472 functions with external sense and gain-set-
ting resistors. Both devices have a current output that
can be converted to a ground-referred voltage with a
single resistor, allowing a wide range of battery volt-
ages and currents.
An open-collector SIGN output indicates current-flow
direction, so the user can monitor whether a battery is
being charged or discharged. Both devices operate
from 3V to 36V, draw less than 100µA over tempera-
ture, and include a 18µA max shutdown mode.
________________________Applications
Portable PCs:
Notebooks/Subnotebooks/Palmtops
Smart Battery Packs
Cellular Phones
Portable Phones
Portable Test/Measurement Systems
Battery-Operated Systems
Energy Management Systems
__________Typical Operating Circuit
____________________________Features
o Complete High-Side Current Sensing
o Precision Internal Sense Resistor (MAX471)
o 2% Accuracy Over Temperature
o Monitors Both Charge and Discharge
o 3A Sense Capability with Internal Sense Resistor
(MAX471)
o Higher Current-Sense Capability with External
Sense Resistor (MAX472)
o 100µA Max Supply Current
o 18µA Max Shutdown Mode
o 3V to 36V Supply Operation
o 8-Pin DIP/SO Packages
______________Ordering Information
PART
MAX471CPA
MAX471CSA
MAX471EPA
MAX471ESA
MAX472CPA
MAX472CSA
MAX472EPA
MAX472ESA
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
_________________Pin Configurations
RS+ RS-
RS+ RS-
100k
3V
TO
MAX471
SIGN
36V
SHDN GND
OUT
ILOAD
2000
2k
ILOAD TO
LOAD or CHARGER
LOGIC
SUPPLY
DISCHARGE/CHARGE
VOUT (1V/A)
TOP VIEW
SHDN 1
RS+ 2
RS+ 3
GND 4
MAX471
DIP/SO
8 OUT
7 RS-
6 RS-
5 SIGN
MAX472 Pin Configuration continued on last page.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
1 page  
Precision, High-Side
Current-Sense Amplifiers
____________________________Typical Operating Characteristics (continued)
(Typical Operating Circuit (MAX471) or circuit of Figure 4, RG1 = RG2 = 200Ω, ROUT = 2kΩ (MAX472), TA = +25°C, unless
otherwise noted.)
MAX472
ERROR vs. SENSE VOLTAGE
25
MAX471
NOISE vs. LOAD CURRENT
0.5
15
VRG1-VRG2
5
0
-5
VRG2-VRG1
-15
0.4
0.3
0.2
0.1
-25
0.1
1 10 100
VSENSE (mV)
1000
0
1mA
10mA
100mA
ISENSE
1A
MAX471
0mA to 100mA TRANSIENT RESPONSE
LOAD
CURRENT
50mA/div
0A
VOUT
50mV/div
100µs/div
VCC = 10V, ROUT = 2kΩ 1%, SIGN PULL-UP = 50kΩ 1%
MAX471
START-UP DELAY
MAX471
-100mA to +100mA TRANSIENT RESPONSE
LOAD
0A CURRENT
100mA/div
VOUT
50mV/div
50mA/div
100µs/div
VCC = 10V, ROUT = 2kΩ 1%, SIGN PULL-UP = 50kΩ 1%
SIGN
50mV/div
MAX471
0A TO 3A TRANSIENT RESPONSE
ILOAD
1A/div
VOUT
500mV/div
VSHDN
5V/div
VOUT
10mV/div
10µs/div
ILOAD = 1A, ROUT = 2kΩ 1%
ROUT = 2kΩ 1%
10µs/div
_______________________________________________________________________________________ 5
5 Page 
Precision, High-Side
Current-Sense Amplifiers
require, given the full-scale IOUT determined by
RSENSE, RG1, and RG2. The high compliance of OUT
permits using ROUT values up to 10kΩ with minimal
error. Values above 10kΩ are not usually recommend-
ed. The impedance of OUT’s load (e.g., the input of an
op amp or ADC) must be much greater than ROUT
(e.g., 100 x ROUT) to avoid degrading the measure-
ment accuracy.
High-Current Measurement
The MAX472 can achieve higher current measurements
than the MAX471 can. Low-value sense resistors may
be paralleled to obtain even lower values, or the PC
board trace may be adjusted for any value.
An alternative method is to connect several MAX471s in
parallel and connect the high-impedance current-
source OUT pins together to indicate the total system
current (Figure 3). Pay attention to layout to ensure
equal IR drops in the paralleled connection. This is
necessary to achieve equal current sharing.
Power-Supply Bypassing and Grounding
The MAX471 has been designed as a “high side” (posi-
tive terminal) current monitor to ease the task of
grounding any battery charger, thermistor, etc. that
may be a part of the battery pack. Grounding the
MAX471 requires no special precautions; follow the
same cautionary steps that apply to the system as a
whole. High-current systems can experience large volt-
age drops across a ground plane, and this drop may
add to or subtract from VOUT. For highest current-mea-
surement accuracy, use a single-point “star” ground.
The MAX471/MAX472 require no special bypassing,
and respond quickly to transient changes in line cur-
rent. If the noise at OUT caused by these transients is a
problem, you may want to place a 1µF capacitor at the
OUT pin to ground. You can also place a large capaci-
tor at the RS- terminal (or “load” side of the MAX472) to
decouple the load and, thereby, reduce the current
transients. These capacitors are not required for
MAX471/MAX472 operation or stability, and their use
will not degrade performance.
For the MAX472, the RG1 and RG2 inputs can be fil-
tered by placing a capacitor (e.g., 1µF) between them
to average the sensed current.
MAX471 Layout
The MAX471 must be soldered in place, since sockets
can cause uneven current sharing between the RS+
pins (pins 2 and 3) and the RS- pins (pins 6 and 7),
resulting in typical errors of 0.5%.
In order to dissipate sense-resistor heat from large
sense currents, solder the RS+ pins and the RS- pins to
large copper traces. Keep the part away from other
heat-generating devices. This procedure will ensure
continuous power dissipation rating.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX472.PDF ] | |
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