HV7801K1 데이터 시트보기 (PDF) - Supertex Inc
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HV7801K1 Datasheet PDF : 5 Pages
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HV7801
Block Diagram
VSENSE
ISENSE
Typical use is measurement of line or load current for purpose
of overcurrent protection, metering and current regulation.
RSENSE
RP
(Optional,
IN
LOAD see text)
RA
High side current sensing, as opposed to ground referenced
or low side current sensing, is desirable or required when:
► The current to be measured does not flow in a circuit
associated with ground.
► The measurement at ground level can lead to ambiguity
due to changes in the grounding arrangement during
field use.
► The introduction of a sense resistor in the system ground
is undesirable due to issues with safety, EMI, or signal
degradation due to common impedance coupling.
Bias
Circuits
VOUT
OUT
RB
HV7801
GND
Principle of Operation
The operational amplifier and MOSFET forces the voltage
across RA to track VSENSE within the limit of the offset voltage
of the opamp, i.e. VRA = VSENSE.
The current through RA returns to ground through RB.
RA and RB are integrated, exhibiting tight matching and
excellent tracking. By design, RB is five times larger than RA.
Consequently, VRB is five times larger than VRA, thus resulting
in a voltage gain of 5.
OUT Pin Loading Effects
Application Information
General
Note that the OUT pin has an typical output resistance of
16.5kΩ. Loading the output causes the voltage gain to drop
and rise/fall times to increase.
For example, assuming output resistance is 16.5kΩ, the load
resistance should exceed 16.5MΩ in order to limit the drop in
gain to 1 part in 1000.
The HV7801 high side current monitor IC features accurate
current sensing, small size, low component count, low power
consumption, exceptional input voltage range, ease of use
and low cost.
Again assuming output resistance is 16.5kΩ, capacitive
loading of 6pF results in a response pole with a time constant
of 100ns, not high enough to materially affect the output rise
and fall times (about 700ns).
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