HV7802
High Side Current Monitor
8V to 450V, Configurable Output
Features
►
►
►
►
►
►
Supply voltage 8V to 450V
Configurable as a current or voltage output device
Maximum sense amplifier offset of 15mV
Max V
SENSE
of 500mV
Fast rise and fall times, from 700ns to 2.0µs
Maximum quiescent current of 50µA
General Description
The HV7802 high side current monitor IC contains a
transconductance amplifier which translates a high side
current measurement voltage into an output current with
resistor programmable transconductance gain. An optional
second resistor transforms this output current into an output
voltage with an overall voltage gain set by the ratio of the two
resistors.
The measurement voltage typically originates at a current
sense resistor, which is located in a “high side” circuit, for
example a circuit not directly associated with ground.
This monitor IC features a very wide input voltage range,
configurable gain, small size, low component count, low power
consumption, ease of use, and low cost. Offline applications,
battery, and portable applications can be served equally well
due to the wide input voltage range and the low quiescent
current.
Applications
►
SMPS current monitor
►
Battery current monitor
►
Motor control
Typical Application Circuit
V
SENSE
I
SENSE
8V to 450V Input
R
SENSE
R
A
IN
RA
R
P
LOAD
R
I
OUT
= V
SENSE
/ R
A
V
OUT
= R
B
● I
OUT
G
V
= R
B
/ R
A
HV7802
GND
OUT
V
OUT
I
OUT
R
B
V
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
HV7802
Ordering Information
Device
HV7802
3.00x3.00mm body
1.10mm height (max)
0.65mm pitch
8-Lead MSOP
HV7802MG-G
-G indicates package is RoHS compliant (‘Green’)
Absolute Maximum Ratings
Parameter
V
IN
, V
LOAD
V
OUT
V
SENSE
I
LOAD
Operating ambient temperature
Operating junction temperature
Storage temperature
Value
-0.5V to +450V
-0.5V to +10V
-0.5V to +5.0V
±10mA
-40°C to +85°C
-40°C to +125°C
-65°C to +150°C
Pin Configuration
GND
8
NC
7
OUT
6
NC
5
1
2
RA
3
4
IN
LOAD
NC
8-Lead MSOP
(top view)
Product Marking
Top Marking
Absolute maximum ratings are those values beyond which damage to
the device may occur. Functional operation under these conditions is not
implied. Continuous operation of the device at the absolute rating level
may affect device reliability. All voltages are referenced to device ground.
7802
LLLL
Bottom Marking
Thermal Resistance
Package
8-Lead MSOP
Note:
Thermal testboard per JEDEC JESD51-7
θ
ja
220
O
C/W
YYWW
L = Lot Number
YY = Year Sealed
WW = Week Sealed
= “Green” Packaging
8-Lead MSOP
= V
IN
- V
LOAD
, V
IN
= 8.0V to 450V)
Electrical Characteristics
(T = 25°C unless otherwise specified, V
A
SENSE
Sym
Parameter
Min
Typ
Max
Units
Conditions
Supply
V
IN
I
Q
Supply voltage
Quiescent supply current
8.0
-
-
-
450
50
V
µA
*
-
---
V
IN
= 8V to 450V, V
SENSE
= 0mV
Input and Output
I
OUT
Ouput current
Output voltage,
R
A
= R
B
= 5.000kΩ
-
0
V
OUT
79
177
470
-
-
-
-
-
200
15
121
223
530
mV
-
µA
-
---
V
SENSE
= 0mV
V
SENSE
= 100mV
V
SENSE
= 200mV
V
SENSE
= 500mV
Dynamic Characteristics
t
RISE
t
FALL
*
Output rise time, 10% to 90%
Output fall time, 90% to 10%
-
-
-
0.7
-
0.7
-
2.0
2.0
µs
µs
-
-
V
SENSE
step 5.0mV to 500mV
V
SENSE
step 0mV to 500mV
V
SENSE
step 500mV to 0mV
Values apply over the full temperature range.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
2
HV7802
Block Diagram
V
SENSE
I
SENSE
►
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 caused by common impedance coupling.
R
SENSE
R
P
(Optional,
see text)
LOAD
R
A
IN
RA
Principle of Operation
Bias
Circuits
The operational amplifier forces the voltage across R
A
to
track V
SENSE
, therefore, V
RA
= V
SENSE
. Transconductance gain
is equal to (1/R
A
).
I
RA
flows from the OUT pin to low side circuitry. Current to
voltage conversion can be accomplished by a resistor, R
B
,
as shown in the block diagram, with a transimpedance gain
equal to R
B
.
Typically we would like to exploit the full current capability of
the transimpedance amplifier. A R
A
of 5kΩ will provide this
current, assuming a full scale sense voltage of 500mV and a
full scale sense current of 100µA.
In a voltage output application, the output resistor R
B
is
determined by the desired overall voltage gain of (R
B
/ R
A
).
For example, a R
B
of 10kΩ results in a voltage gain of two.
HV7802
GND
OUT
RB
V
OUT
Application Information
General
The HV7802 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.
Typical use is measurement of line and load current for
purpose of overcurrent protection, metering and current
regulation.
High side current sensing, as opposed to ground referenced
or low side current sensing, is desirable or required when:
OUT Pin Loading Effects
Note that the output is not buffered having an output
impedance equal to R
B
. Loading of the output causes voltage
gain to drop and rise and fall times to increase.
For example, assume a gain of one, using R
A
= R
B
= 5kΩ. In
this case the load resistance should exceed 5MΩ in order to
limit the gain drop to 1 part in 1000.
Assuming an output resistance of 5kΩ, a capacitive load of
20pF results in a load pole with a time constant of 100ns,
not enough to materially affect the output rise and fall time
(about 700ns).
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
3
HV7802
Sense Resistor Considerations
Limit the sense resistor voltage to 500mV during normal
operating conditions. Limit the power dissipation in the sense
resistor to suit the application; a high sense voltage benefits
accuracy, but may result in high power dissipation as well.
Consider the use of Kelvin connections for applications where
considerable voltage drops may occur in the PCB traces.
A layout pattern, which minimizes voltage drops across the
sense lines is shown below.
+ V
SENSE
Transient Protection
Add a protection resistor (R
P
) in series with the LOAD pin if
V
SENSE
can exceed 5V in positive sense or 600mV in negative
sense, whether in steady state or in transient conditions.
A large V
SENSE
may occur during system startup or shutdown
when charging and discharging large capacitors. V
SENSE
may
be large due to fault conditions, such as short circuit or a
broken or missing sense resistor.
An internal 5V Zener diode with a current rating of 10mA
protects the sense amplifier inputs. The block diagram
shows the orientation of this diode. The Zener diode provides
clamping at 5V for a positive V
SENSE
and at 600mV for a
negative V
SENSE
.
Limit the Zener current to 10mA under worst case conditions.
A 100kΩ resistor limits the maximum Zener diode current to
4.5mA when V
SENSE
is 450V, whether positive or negative.
Note that the protection resistor may affect bandwidth.
The resistor forms a RC network with the trace and pin
capacitance at the LOAD pin. For example, capacitance of
5pF results in a time constant of 500ns.
The protection resistor may cause an offset voltage due to
bias current at the LOAD input. A 100kΩ protection resistor
could cause an offset of 100µV, or 0.2% of full scale, under
worst case bias current. Note that bias current is nominally
zero since LOAD is a high impedance CMOS input, resulting
in zero bias current induced offset voltage.
-
R
SENSE
IN
LOAD
Choose a low inductance type sense resistor if preservation
of bandwidth is important. Kelvin connections help by
minimizing the inductive voltage drops as well. The inductive
voltage drop may be substantial when operating at high
frequency. A trace or component inductance of just 10nH
contributes an impedance of 6.2mΩ at 100kHz, which
constitutes a 6% error when using a 100mΩ sense resistor.
Pin Description
Pin #
1
2
3
4
5
6
7
8
Pin Name
IN
RA
LOAD
NC
NC
OUT
NC
GND
Description
Sense amplifier input and supply.
Provides gain setting of the transconductance amplifier. Connect gain setting resistor
(R
A
) between Pin 1 and Pin 2.
Sense amplifier input. High impedance input with Zener diode protection. Add an
external protection resistor in series with LOAD if V
SENSE
exceeds the range of -600mV
to +5V.
No Connect. This pin must be left floating for proper operation
No Connect. This pin must be left floating for proper operation.
Output of the transconductance amplifier. Output current to output voltage conversion
can be accomplished through addition of an external resistor (R
B
) at this pin. Overall
voltage gain is determined by the ratio of R
B
to R
A
.
No connect. This pin must be left floating for proper operation.
Supply return.
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
●
Tel: 408-222-8888
●
www.supertex.com
4
HV7802
8-Lead MSOP Package Outline (MG)
D
8
E
E1
Note 1
(Index Area
D/2 x E1/2)
3.00x3.00mm body, 1.10mm height (max), 0.65mm pitch
θ1 (x4)
L2
Gauge
Plane
1
L
L1
θ
Seating
Plane
Top View
A
View B
View B
A
A2
Seating
Plane
A1
e
b
A
Side View
View A-A
Note:
1. A Pin 1 identifier must be located in the index area indicated. The Pin 1 Identifier can be: a molded mark/identifier; an embedded metal marker; or
a printed indicator.
Symbol
Dimension
(mm)
MIN
NOM
MAX
A
0.75*
-
1.10
A1
0.00
-
0.15
A2
0.75
0.85
0.95
b
0.22
-
0.38
D
2.80*
3.00
3.20*
E
4.65*
4.90
5.15*
E1
2.80*
3.00
3.20*
e
0.65
BSC
L
0.40
0.60
0.80
L1
0.95
REF
L2
0.25
BSC
θ
0
O
-
8
O
θ1
5
O
-
15
O
JEDEC Registration MO-187, Variation AA, Issue E, Dec. 2004.
* This dimension is not specified in the original JEDEC drawing. The value listed is for reference only.
Drawings are not to scale.
Supertex Doc. #:
DSPD-8MSOPMG, Version F082008.
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline
information go to
http://www.supertex.com/packaging.html.)
Supertex inc.
does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives an
adequate “product liability indemnification insurance agreement.”
Supertex inc.
does not assume responsibility for use of devices described, and limits its liability to the
replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and specifications
are subject to change without notice. For the latest product specifications refer to the
Supertex inc.
website: http//www.supertex.com.
©2008
All rights reserved. Unauthorized use or reproduction is prohibited.
Doc.# DSFP-HV7802
A092308
5
1235 Bordeaux Drive, Sunnyvale, CA 94089
Tel: 408-222-8888
www.supertex.com
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