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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 5mV Max VSENSE of 500mV Fast rise and fall times, from 700ns to 1.4s Maximum quiescent current of 50A
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
VSENSE RSENSE ISENSE
8V to 450V Input
RA
RP
IN IOUT = VSENSE / RA VOUT = RB IOUT GV = RB / RA GND
RA
LOAD
HV7802
OUT VOUT IOUT RB V
R
HV7802
Ordering Information
Device
HV7802
Package Option 8-Lead MSOP
HV7802MG-G
-G indicates package is RoHS compliant (`Green')
Absolute Maximum Ratings
Parameter VIN, VLOAD VOUT VSENSE ILOAD Operating ambient temperature Operating junction temperature Storage temperature Value -0.5V to +450V -0.5V to +10V -0.5V to +5.0V 10mA 0C to +70C -40C to +125C -65C to +150C
Pin Configuration
GND 8 NC 7 OUT 6 NC 5
1 IN
2
3
4
RA LOAD NC
8-Lead MSOP
(top view)
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.
Product Marking
Top Marking
7802 LLLL
Bottom Marking
Thermal Resistance
Package 8-Lead MSOP
Note: Thermal testboard per JEDEC JESD51-7
ja 220 OC/W
YYWW
L = Lot Number YY = Year Sealed WW = Week Sealed = "Green" Packaging
8-Lead MSOP
A SENSE
Electrical Characteristics (T = 25C unless otherwise specified, V
Symbol Parameter Min Typ
= VIN - VLOAD, VIN = 8.0V to 450V)
Max
Units
Conditions
Supply
VIN IQ Supply voltage* Quiescent supply current 8.0 450 50 V A --VIN = 8V to 450V, VSENSE = 0mV
Input and Output
IOUT Ouput current Output voltage, RA = RB = 5.000k 0 VOUT 89 188 485 200 10 111 212 515 mV A --VSENSE = 0mV VSENSE = 100mV VSENSE = 200mV VSENSE = 500mV
Dynamic Characteristics
tRISE tFALL Output rise time, 10% to 90% Output fall time, 90% to 10% 0.7 0.7 0.8 1.4 0.8 s s VSENSE step 5.0mV to 500mV VSENSE step 0mV to 500mV VSENSE step 500mV to 0mV
*Values apply over the full temperature range.
2
HV7802
Block Diagram
VSENSE ISENSE
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 RP (Optional, see text)
RA IN RA
LOAD
Principle of Operation
The operational amplifier forces the voltage across RA to track VSENSE, therefore, VRA = VSENSE. Transconductance gain is equal to (1/RA). IRA flows from the OUT pin to low side circuitry. Current to voltage conversion can be accomplished by a resistor, RB, as shown in the block diagram, with a transimpedance gain equal to RB.
VOUT
Bias Circuits
HV7802
GND OUT
RB
Typically we would like to exploit the full current capability of the transimpedance amplifier. A RA of 5k will provide this current, assuming a full scale sense voltage of 500mV and a full scale sense current of 100A. In a voltage output application, the output resistor RB is determined by the desired overall voltage gain of (RB / RA). For example, a RB of 10k results in a voltage gain of two.
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 RB. Loading of the output causes voltage gain to drop and rise and fall times to increase. For example, assume a gain of one, using RA = RB = 5k. In this case the load resistance should exceed 5M in order to limit the gain drop to 1 part in 1000. Assuming an output resistance of 5k, 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).
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.
+ VSENSE
Transient Protection
Add a protection resistor (RP) in series with the LOAD pin if VSENSE can exceed 5V in positive sense or 600mV in negative sense, whether in steady state or in transient conditions. A large VSENSE may occur during system startup or shutdown when charging and discharging large capacitors. VSENSE 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 VSENSE and at 600mV for a negative VSENSE.
-
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 6.2m at 100kHz, which constitutes a 6% error when using a 100m sense resistor.
Limit the Zener current to 10mA under worst case conditions. A 100k resistor limits the maximum Zener diode current to 4.5mA when VSENSE 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 100k protection resistor could cause an offset of 100V, 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.
Pin Description
Pin # 1 2 Pin Name IN RA Description Sense amplifier input and supply. Provides gain setting of the transconductance amplifier. Connect gain setting resistor (RA) 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 VSENSE 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 (RB) at this pin. Overall voltage gain is determined by the ratio of RB to RA. No connect. This pin must be left floating for proper operation. Supply return.
3 4 5 6 7 8
LOAD NC NC OUT NC GND
4
HV7802
8-Lead MSOP Package Outline (MG)
3x3mm body, 1.10mm height (max), 0.65mm pitch
D 8
1 (x4)
E E1
Note 1 (Index Area D1/2 x E1/2) L L2 Gauge Plane
1
L1
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 may be either a mold, or an embedded metal or marked feature.
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
0
O
1 5O 15O
8O
JEDEC Registration MO-187, Variation AA, Issue E, Dec. 2004. Drawings not to scale.
(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.)
Doc.# DSFP-HV7802 A042307
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