View HV7800_821938.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Supertex inc.
High Side Current Monitor
Features
450V Maximum supply voltage Voltage output device 1% Typical gain accuracy 500mV Maximum VSENSE Fast response: 700ns rise and fall time 50A Quiescent current (max.)
HV7800
Initial Release
General Description
The HV7800 is a high side current monitor IC, senses the voltage across an external current resistor located in the power or "high" side of the and translates this voltage to a ground referenced at a gain of one. which sense circuit circuit
Applications
LED driver current monitor SMPS current monitor Battery current monitor Motor controls
The HV7800 has a wide operating range of 3V-450VDC, which enables its use in DC power systems of 12V/24V/ 48V, and in AC systems operating at voltages from 85VAC to 265VAC. The fast response time of the HV7800 allows use of this current monitor in the feedback loop of a switching power supply or in LED driver applications.
Typical Application Circuit
VSENSE 400VDC Input
3
ILOAD
RSENSE
2 1
LOAD
HV7800
4 5
VOUT = ILOAD * RSENSE
NR031306
Supertex inc.
* 1235 Bordeaux Drive, Sunnyvale, CA 94089 * Tel: (408) 222-8888 * FAX: (408) 222-4895 * www.supertex.com
1
HV7800
Ordering Information
DEVICE HV7800K1-G
-G indicates package is RoHS compliant (`Green')
Package Options 5-Lead SOT-23
Absolute Maximum Ratings
Parameter IN LOAD OUT Operating Ambient Temperature1 Operating Junction Temperature Storage Temperature SOT23-5 Package Thermal Resistance Value -0.5V to +450V -0.5V to +450V -0.5V to +10V -40C to +85C -40C to +125C -65C to +150C 260 K/W
Pinout
LOAD N/C IN
1 2 3 4 5
OUT
GND
HV7800K1
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1 Limited by package dissipation.
Electrical Characteristics
(Voltages referenced to GND, VIN = 10V, TA = 25C, unless otherwise noted. Values of parameters marked with a * apply over the full temperature range.)
Symbol
Parameter
Min
Typ
Max
Units
Conditions
ESD Characteristics, IN, LOAD ESD Supply VIN IQ Supply voltage Quiescent supply current 10 10 450 50 * V A --VIN = 400V, VSENSE = 0mV Human body model 2.0 kV 1.5k, 100pF
Input and Output Characteristics ILOAD ROUT Input current to LOAD pin OUT pin output resistance -1.0 2.60 0 94 VOUT Output Voltage 193 490 Dynamic Characteristics tRISE tFALL Output rise time, 10% to 90% Output fall time, 90% to 10% 700 700 ns ns VSENSE step 0mV to 500mV VSENSE step 500mV to 0mV 207 510 3.30 1.0 4.0 5.0 106 mV * nA k VSENSE = 500mV --VSENSE = 0mV VSENSE = 100mV VSENSE = 200mV VSENSE = 500mV
NR031306
2
HV7800
Typical Performance Characteristics
160 0
120 -20 80
CMRR (dB)
Gain (dB)
10m 0.1 1.0 10 100 1K 10K 100K 1M 10M
40
-40
0
-60
-40 1.0M
Frequency (Hz)
10m
0.1
1
10
100
1K
10K
100K
1M
10M
Frequency (Hz)
Common Mode Rejection Ratio vs Frequency
Gain vs Frequency
0.5 0.5 0.4 0.4 VSENSE = 400mV VSENSE = 500mV
VSENSE, VOUT (V)
0.3 VSENSE = 5mV-500mV 0.2
VOUT Voltage(V)
0.3 VSENSE = 300mV 0.2 VSENSE = 200mV 0.1 VSENSE = 100mV
0.1
0 2 4 6 8 10 12
0 0 2 4 6 8 10
time (s)
VIN Voltage(V)
Step Response (5.0mV to 500mV)
Output Characteristics (VOUT vs VIN)
NR031306
3
HV7800
Block Diagram
RSENSE ILOAD
IN
3 1
LOAD
RA
BIAS CKTS
5
OUT
RB
4
GND
Pin Description
Pin 1 2 3 4 5 Name LOAD N/C IN GND OUT Description This pin is an input sense pin that connects to the negative (-) side of sense resistor, RSENSE. The negative side denotes the system load end of the sense resistor. No Connection Positive supply. Input voltage range is 3.0 to 450V. This pin is an input sense pin that connects to the positive (+) side of sense resistor, RSENSE. This pin is connected to the GND or return of the system. Output Voltage referenced to GND terminal. The voltage at OUT will be equal to VSENSE. The output impedance of this pin is typically 3.3 k.
LOAD N/C IN
1 2 3
5
OUT
4
GND
HV7800K1
NR031306
4
HV7800
Application Information
General
The HV7800 offers high side current sensing featuring accuracy, small size, low component count, low power consumption, ease of use and low cost. The input voltage rating of 450V extends the use to off-line applications. The HV7800 allows measurement of line or load current for purpose of overcurrent protection, current metering and current regulation. High side current sensing, as opposed to ground or low-side sensing, is desirable or required when: * * The current to be measured does not flow in a circuit associated with ground. The addition of resistance in the grounding system will cause issues with safety, EMI, or will lead to signal degradation due to common impedance coupling.
RLOAD CLOAD RSENSE ILOAD
IN
LOAD
HV7800
GND OUT ROUT = 3.3k 30%
Sense Resistor Considerations
The choice of value of the sense resistor entails a tradeoff between power dissipation from the sense resistor and accuracy. Power dissipation from the sense resistor is equal to (VSENSE * ILOAD). It is generally desirable to maximize VSENSE to enhace accuracy, but not to the extent that power dissipation from the sense resistor becomes objectionable. Consider the use of Kelvin connections for applications with a large load current. A typical layout pattern, which minimizes voltage drops across the sense lines is shown below:
Principle of Operation
The operational amplifier and associated MOSFET, as shown in the block diagram, force a current through resistor RA such that VRA is equal to VSENSE. The current through RA flows to ground through RB and develops an output voltage VOUT, which is equal to VSENSE, given that RA and RB have equal resistance. Note that the output is not buffered, having an output resistance of 3.3k nominal. Loading of the output will affect gain accuracy and / or bandwidth. Assume in the following that ROUT = 4k. To limit gain error to say 1 part in 1000, the external load impedance should exceed 4M. Capacitive loading forms a load pole. The break frequency follows from:
Sense Resistor
f=
1 2 * *
where
=
(R
B
// RLOAD * CLOAD
)
VSENSE
Preservation of bandwidth requires careful attention to trace layout and choice of sense resistor. Note that the resistance of the sense resistor is typically small, and that both the impedence of printed circuit board traces and the equivalent series inductance of the sense resistance can be a major part of the total sense/impedence at high frequency operation. An inductance of just 1nH contributes an impedence of 3m at 500kHz.
E.g. let RLOAD = and CLOAD = 1nF, then the load pole is located at 38.8kHz, giving rise and fall times of 8.8us.
NR031306
5
HV7800
Protection of the LOAD input In situations where the sense voltage can significantly exceed 500mV, the LOAD input to the differential amplifier should be protected by the addition of a protection resistor and two diodes as shown below:
RSENSE ISURGE
An excessive sense voltage might occur when line or load current is significantly larger during the startup or shutdown event, or during overcurrent or short circuit events. A large differential voltage can also exist if the sense resistor fails open, or is inadvertently not installed.
RPROTECT
IN
LOAD
HV7800
GND OUT
5-Lead SOT-23 (K1) Package Outline
2.80 3.05
1.50 1.75
2.60 3.00
All dimensions are in millimeters Legend: min max
Pin 1 0.95ref 1.90ref Top View 0.90 1.30 0.90 1.45 0.00 0.15 0.30 0.50 0.09 0.20 0.30 0.55 Front View
Side View
(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 its products for use in such applications, unless it receives an adequate "product liability indemnification insurance agreement". Supertex 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 or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the Supertex website: http//www.supertex.com.
(c)2006 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited.
Supertex inc.
1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 222-8888 / FAX: (408) 222-4895
Doc.# DSFP - HV7800 NR031306
www.supertex.com
6

▲Up To Search▲

Price & Availability of HV7800

	To Download HV7800 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .