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PDF MAX4172EUA Data sheet ( Hoja de datos )
| Número de pieza | MAX4172EUA | |
| Descripción | Low-Cost / Precision / High-Side Current-Sense Amplifier | |
| Fabricantes | Maxim Integrated | |
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19-1184; Rev 0; 12/96
Low-Cost, Precision, High-Side
Current-Sense Amplifier
_______________General Description
The MAX4172 is a low-cost, precision, high-side current-
sense amplifier for portable PCs, telephones, and other
systems where battery/DC power-line monitoring is criti-
cal. High-side power-line monitoring is especially useful in
battery-powered systems, since it does not interfere with
the battery charger’s ground path. Wide bandwidth
and ground-sensing capability make the MAX4172
suitable for closed-loop battery-charger and general-
purpose current-source applications. The 0V to 32V input
common-mode range is independent of the supply volt-
age, which ensures that current-sense feedback remains
viable, even when connected to a battery in deep dis-
charge.
To provide a high level of flexibility, the MAX4172 func-
tions with an external sense resistor to set the range of
load current to be monitored. It has a current output that
can be converted to a ground-referred voltage with a sin-
gle resistor, accommodating a wide range of battery volt-
ages and currents.
An open-collector power-good output (PG) indicates
when the supply voltage reaches an adequate level to
guarantee proper operation of the current-sense amplifi-
er. The MAX4172 operates with a 3.0V to 32V supply
voltage, and is available in a space-saving, 8-pin µMAX
or SO package.
________________________Applications
Portable PCs: Notebooks/Subnotebooks/Palmtops
Battery-Powered/Portable Equipment
Closed-Loop Battery Chargers/Current Sources
Smart-Battery Packs
Portable/Cellular Phones
Portable Test/Measurement Systems
Energy Management Systems
__________________Pin Configuration
TOP VIEW
RS+ 1
RS- 2
N.C. 3
N.C. 4
MAX4172
8 V+
7 PG
6 OUT
5 GND
____________________________Features
o Low-Cost, High-Side Current-Sense Amplifier
o ±0.5% Typical Full-Scale Accuracy Over
Temperature
o 3V to 32V Supply Operation
o 0V to 32V Input Range—Independent of
Supply Voltage
o 800kHz Bandwidth [VSENSE = 100mV (1C)]
200kHz Bandwidth [VSENSE = 6.25mV (C/16)]
o Available in Space-Saving µMAX and SO
Packages
______________Ordering Information
PART
TEMP. RANGE
MAX4172ESA
-40°C to +85°C
MAX4172EUA
-40°C to +85°C
*Contact factory for availability.
PIN-PACKAGE
8 SO
8 µMAX*
__________Typical Operating Circuit
UNREGULATED
DC SUPPLY
3V TO 32V
LOW-COST
SWITCHING
REGULATOR
RSENSE
50mΩ
VSENSE
0V TO 32V
ANALOG OR
LOGIC SUPPLY
2A
RS+ RS-
V+
PG
MAX4172
OUT
GND
FEEDBACK LOOP
VOUT = 500mV/A
100k
POWER GOOD LOAD/
BATTERY
IOUT =
VSENSE / 100Ω
ROUT
1k
µMAX/SO
LOW-COST BATTERY CHARGER/CURRENT SOURCE
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
1 page  
Low-Cost, Precision, High-Side
Current-Sense Amplifier
____________________________Typical Operating Characteristics (continued)
(V+ = +12V, VRS+ = 12V, ROUT = 1kΩ, TA = +25°C, unless otherwise noted.)
START-UP DELAY
MAX4172-10
V+ to PG POWER-UP DELAY
MAX4172-11
VOUT
500mV/div
GND
PG
2V/div
GND
V+
2V/div
GND
VSENSE = 100mV
5µs/div
V+
2V/div
GND
10µs/div
100kΩ PULL-UP RESISTOR FROM PG TO +4V
______________________________________________________________Pin Description
PIN NAME
FUNCTION
1 RS+ Power connection to the external sense resistor. The “+” indicates the direction of current flow.
2 RS- Load-side connection for the external sense resistor. The “-” indicates the direction of current flow.
3, 4
N.C.
No Connect. No internal connection. Leave open or connect to GND.
5
GND
Ground
6
OUT
Current Output. OUT is proportional to the magnitude of the sense voltage (VRS+ - VRS-). A 1kΩ
resistor from OUT to ground will result in a voltage equal to 10V/V of sense voltage.
7
PG
Power Good Open-Collector Logic Output. A low level indicates that V+ is sufficient to power the
MAX4172, and adequate time has passed for power-on transients to settle out.
8 V+ Supply Voltage Input for the MAX4172
_______________Detailed Description
The MAX4172 is a unidirectional, high-side current-sense
amplifier with an input common-mode range that is inde-
pendent of supply voltage. This feature not only allows
the monitoring of current flow into a battery in deep dis-
charge, but also enables high-side current sensing at
voltages far in excess of the supply voltage (V+).
The MAX4172 current-sense amplifier’s unique topolo-
gy simplifies current monitoring and control. The
MAX4172’s amplifier operates as shown in Figure 1.
The battery/load current flows through the external
sense resistor (RSENSE), from the RS+ node to the RS-
node. Current flows through RG1 and Q1, and into the
current mirror, where it is multiplied by a factor of 50
before appearing at OUT.
To analyze the circuit of Figure 1, assume that current
flows from RS+ to RS-, and that OUT is connected to
GND through a resistor. Since A1’s inverting input is
high impedance, no current flows though RG2 (neglect-
ing the input bias current), so A1’s negative input is
equal to VSOURCE - (ILOAD x RSENSE). A1’s open-loop
gain forces its positive input to essentially the same
voltage level as the negative input. Therefore, the drop
across RG1 equals ILOAD x RSENSE. Then, since IRG1
_______________________________________________________________________________________ 5
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| PDF Descargar | [ Datasheet MAX4172EUA.PDF ] | |
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