MAX4210_05 Datasheet, PDF (20/32 Pages) Maxim Integrated Products – High-Side Power and Current Monitors

High-Side Power and
Current Monitors
The common-mode voltage range is +4V to +28V and
independent of the supply voltage. With this feature, the
device can monitor the output current of a high-voltage
source while running at a lower system voltage typically
between 2.7V and 5.5V.
The MAX4211 has a current-sense amplifier output. The
voltage at IOUT is proportional to the voltage across
V_SENSE:
V_IOUT = A_VIOUT x V_SENSE
where V_SENSE is the voltage across RS+ and RS-, and
A_VIOUT is the amplifier gain of the device given in Table 1.
Analog Multiplier
The MAX4210/MAX4211 integrate an analog multiplier
that enables real-time monitoring of power delivered to
a load. The voltage proportional to the load current is
fed to one input of the multiplier and a voltage propor-
tional to the source voltage is fed to the other. The ana-
log multiplier multiplies these two voltages to obtain an
output voltage proportional to the load power. The ana-
log multiplier is designed only to operate in the positive
quadrant, that is, the inputs and outputs are always
positive voltages.
For the MAX4210D/E/F and MAX4211D/E/F, the analog
multiplier full-scale input at IN is approximately 1V. This
independent multiplier input allows greater design flexi-
bility when using an external voltage-divider. For the
MAX4210A/B/C and MAX4211A/B/C, an integrated volt-
age-divider divides the source voltage at the RS+ pin
by a nominal value of 25 and passes this voltage to the
multiplier. Thus, the full-scale input voltage at RS+ is
25V. The integrated, trimmed resistor-dividers reduce
external component count and cost.
The voltage output at POUT is proportional to the output
power:
For the MAX4210A/B/C and MAX4211A/B/C:
V_POUT = A_VPOUT x V_SENSE x V_RS+
For the MAX4210D/E/F and MAX4211D/E/F:
V_POUT = A_VPOUT x V_SENSE x V_IN
Table 1. MAX4211 Current-Sense
Amplifier Gain and Full-Scale Sense
Voltage
PART
MAX4211A/D
MAX4211B/E
MAX4211C/F
CURRENT-SENSE
AMPLIFIER GAIN
(A_VIOUT, V/V)
16.67
25.00
40.96
FULL-SCALE
SENSE VOLTAGE
(mV)
150
150
100
where V_SENSE is the voltage across RS+ and RS- and
A_VPOUT is the amplifier gain of the device given in
Table 2.
Internal Comparators (MAX4211)
The MAX4211 features two uncommitted open-drain
output comparators. These comparators can be config-
ured to trip when load current or power reaches a set
limit. They can also be configured as a window com-
parator with wire-OR output. Comparator 1 (COUT1)
features latch-enable (LE) and inhibit (INHIBIT) inputs.
When LE is low, the comparator is transparent (it func-
tions as a regular unlatched comparator). When LE is
high, the comparator output (COUT1) is latched. When
high, the INHIBIT input suspends the comparator oper-
ation and latches the output to the current state. The
operation of INHIBIT is similar to LE, except it has a dif-
ferent input threshold and wider hysteresis. The INHIB-
IT logic-high threshold is 1.21V and logic-low threshold
is 0.6V with 0.6V hysteresis. INHIBIT is useful in pre-
venting the comparator from giving false output during
fast RS+ transients. INHIBIT is generally triggered by
an RC network connected to RS+ (see the Applications
Information). Both comparators have a built-in 300µs
blanking period at power-up to prevent false outputs.
The comparator outputs are open drain and they can
be pulled up to V_CC, RS+, or any voltage less than
+28V. LE and INHIBIT are internally pulled down by a
1µA source.
Table 2. MAX4210/MAX4211 Power-Sense
Amplifier Gain and Full-Scale Sense
Voltage
PART
MAX4210A
MAX4210B
MAX4210C
MAX4210D
MAX4210E
MAX4210F
MAX4211A
MAX4211B
MAX4211C
MAX4211D
MAX4211E
MAX4211F
POWER-SENSE
AMPLIFIER GAIN
(A_VPOUT, 1/V)
0.667
1.000
1.640
16.670
25.000
40.960
0.667
1.000
1.640
16.670
25.000
40.960
FULL-SCALE
SENSE VOLTAGE
(mV)
150
150
100
150
150
100
150
150
100
150
150
100
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