MAX9643TASA+ Maxim Integrated, MAX9643TASA+ Datasheet - Page 8

• Manufacturer Part Number: MAX9643TASA+
• Description: Current Sense Amplifiers 60V High-Speed Prec current-Sense Amp
• Manufacturer: Maxim Integrated
• Series: MAX9643r

Specifications of MAX9643TASA+

• Rohs: yes

The MAX9643 is a high-speed precision current-sense
amplifier ideal for a wide variety of high-performance
industrial and automotive power-supply applications. The
device’s low input offset voltage, tight gain error, and low
temperature drift characteristics allow the use of small-
sense resistors for current measurements to improve
power-supply conversion efficiency and accuracy of mea-
surements. Its fast response allows it to react quickly to
switching currents as is common in power-supply circuits,
and makes it possible to be used as part of control loops.
The unidirectional high-side, current-sense amplifier
also features a wide -1.5V to +60V input common-mode
range. This feature allows monitoring of power-supply
load current even if the rail is shorted to ground. High-
side current monitoring does not interfere with the ground
path of the load being measured, making the IC particu-
larly useful in a wide range of high-reliability systems.
The IC has been designed on a proprietary high-speed
complementary BiCMOS SOI process. This high-voltage
analog process is optimized for excellent AC dynamic
performance, ultra-low noise, wide operating voltage
range, and low-drift signal conditioning circuitry.
An internal charge pump on the part is utilized to provide
two attractive application features:
U Input common-mode voltage range extends to 1.5V
U Output voltage range extends down to true ground.
A 250kHz internal charge pump is used to generate a
negative voltage rail to bias both the input stage and
output stage of the current-sense amplifier. Use a 1FF
ceramic capacitor between the CP1 and CP2 pins of the
IC, and ensure a tight layout to minimize loop area. Using
a 1FF ceramic capacitor from V
good low-noise performance.
It is possible to also connect the V
external -5V power supply. Ensure that this voltage is
lower than the internally generated charge-pump voltage.
The MAX9643 EV kit shows a good example layout. A
representation is shown in Figure 1.
Maxim Integrated
60V High-Speed Precision Current-Sense Amplifier
below ground.
Application Information
Detailed Description
Internal Charge Pump
EE
to GND is essential to
EE
pin directly to an
The use of an internal negative voltage rail for its
input stage allows the current-sense amplifier to extend
its input common-mode voltage below ground without
any crossover inaccuracies. Crossover problems with
precision can occur with alternate architectures of
current-sense amplifiers that use two different input
differential stages to cover the entire operating common-
mode voltage range (either npn/pnp transistors or pnp
transistor and resistor-based input stages).
The minimum input common-mode voltage capability
is dependent on the internal negative voltage rail gener-
ated by the charge pump. Since this negative voltage rail
goes down at low values of V
minimum input common-mode voltage rail is also limited
at low V
The negative input common-mode voltage specification
can be exceeded if the input current is limited to under
5mA. This is typically accomplished by using series
input resistors. The input ESD structure for negative input
common-mode voltages looks like 5 series-connected
diodes. Assuming an on-drop of 0.7V per diode, negative
Figure 1. PCB Layout
TO ADC
CC
Input Common-Mode Voltage Range
.
0.1µF
+
1µF
8
1
CC
MAX9643
7
2
(i.e., when under 5V), the
FROM R
6
3
MAX9643
1µF
SENSE
4
5
8