MAX9928F Maxim, MAX9928F Datasheet - Page 9

• Manufacturer Part Number: MAX9928F
• Description: The MAX9928F/MAX9929F low-cost, uni-/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 1. Functional Diagram
Figure 2. Ideal Transfer Characteristics with 0mV Amplifier Input
Offset Voltage and -1mV Comparator Input Offset Voltage
( ) FOR THE MAX9929F.
*INTERNAL 10kΩ RESISTOR FOR MAX9929_ ONLY.
-3.0
-3.0
LOAD/CHARGER
-0.1V TO +28V
Uni-/Bidirectional, Current-Sense Amplifiers
2.5V TO 5.5V
(V
V
BATT
TO
IN
-1.8
-1.8
)
+
-
_______________________________________________________________________________________
-1.2
-1.2
-0.1V to +28V Input Range, Micropower,
V
RS-
RS+
CC
V
V
SENSE
SENSE
0
0
(mV)
(mV)
1.0
1.0
80kΩ
80kΩ
80kΩ
80kΩ
R
R
R
R
C2
G1
G2
C1
2.0
2.0
3.0
3.0
C
A
For both positive and negative V
current flowing out of the current mirror is equal to:
For the MAX9928F, the transconductance of the device
is trimmed so that I
MAX9929F, the voltage gain of the device is trimmed
so that V
the comparator indicates the polarity of V
The output voltage equation for the MAX9928_ is given
below:
where V
I
the current-sense resistor, R
resistor, and G
(5µA/mV).
The full-scale output voltage range can be set by
changing the R
can be modified to determine the R
particular full-scale range:
OUT is a high-impedance current source and can drive
an unlimited amount of capacitance.
LOAD
S1
= the full-scale current being sensed, R
V
R
OUT
OUT
OUT
OUT
/|V
= (R
= the desired full-scale output voltage,
S2
= (V
Q1
I
OUT
SENSE
OUT
MAX9928F
MAX9929F
m
SENSE
OUT
Current Output (MAX9928F)
= MAX9928F transconductance
resistor value. The above equation
= M x |V
OUT
| = 50V/V. The SIGN output from
)/(I
Q2
GND
x I
CURRENT
/|V
LOAD
MIRROR
LOAD
SENSE
SENSE
OUT
x R
) x (G
V
1MΩ
CC
10kΩ*
= the voltage-setting
| = 5µA/mV. For the
SENSE
SENSE
|/R
SIGN
OUT
OUT
G1
m X
SENSE
x G
required for a
R
voltages, the
OUT
TO ADC
TO μC
m
)
.
SENSE
)
=
9