HV7800

HV7800 SUTEX | Alldatasheet

Document overview

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Technical content

Features

450V Maximum supply voltage Voltage output device 1% Typical gain accuracy 500mV Maximum VSENSE Fast response: 700ns rise and fall time 50µA Quiescent current (max.)

Applications

LED driver current monitor SMPS current monitor Battery current monitor Motor controls General Description The HV7800 is a high side current monitor IC, which senses the voltage across an external current sense resistor located in the power or “high” side of the circuit and translates this voltage to a ground referenced circuit at a gain of one. 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 High Side Current Monitor RSENSE VOUT = ILOAD • RSENSE 400VDC Input HV7800 VSENSE LOAD ILOAD

Ordering Information

-G indicates package is RoHS compliant (‘Green’) Absolute Maximum Ratings Symbol Parameter Min Typ Max Units Conditions ESD Characteristics, IN, LOAD ESD Human body model ±2.0 kV 1.5kΩ, 100pF Supply VIN Supply voltage 450 V --- IQ Quiescent supply current μA VIN = 400V, VSENSE = 0mV Input and Output Characteristics ILOAD Input current to LOAD pin -1.0 1.0 nA VSENSE = 500mV ROUT OUT pin output resistance 2.60 3.30 4.0 kΩ --- VOUT Output Voltage 5.0 mV VSENSE = 0mV 106 VSENSE = 100mV 193 207 VSENSE = 200mV 490 510 VSENSE = 500mV Dynamic Characteristics tRISE Output rise time, 10% to 90% 700 ns VSENSE step 0mV to 500mV tFALL Output fall time, 90% to 10% 700 ns VSENSE step 500mV to 0mV

Electrical Characteristics

(Voltages referenced to GND, VIN = 10V, TA = 25°C, unless otherwise noted. Values of parameters marked with a • apply over the full temperature range.) 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 specifi cations is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 1 Limited by package dissipation. Parameter Value IN −0.5V to +450V LOAD −0.5V to +450V OUT −0.5V to +10V Operating Ambient Temperature1 −40°C to +85°C Operating Junction Temperature −40°C to +125°C Storage Temperature −65°C to +150°C

260 K/W

Typical Performance Characteristics 160 120 -40 10m 0.1 100 10K 100K 10M Frequency (Hz) CMRR (dB) 1.0 1.0M 10m 0.1 100 10K 100K 10M Frequency (Hz) -20 -40 -60 Gain (dB) 0.1 0.2 0.3 0.4 0.5 VSENSE, VOUT (V) time (μs) VSENSE = 5mV-500mV Common Mode Rejection Ratio vs Frequency Gain vs Frequency Step Response (5.0mV to 500mV) Output Characteristics (VOUT vs VIN) 0.1 0.2 0.3 0.4 0.5 VOUT Voltage(V) VIN Voltage(V) VSENSE = 500mV VSENSE = 400mV VSENSE = 300mV VSENSE = 200mV VSENSE = 100mV

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. N/C No Connection IN 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. GND This pin is connected to the GND or return of the system. OUT 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 kΩ. IN LOAD OUT GND HV7800K1 N/C

Application Information

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 fl ow 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. Principle of Operation The operational amplifi er 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 fl ows 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 3.3kΩ nominal. Loading of the output will affect gain accuracy and / or bandwidth. Assume in the following that ROUT = 4kΩ. To limit gain error to say 1 part in 1000, the external load impedance should exceed 4MΩ. Capacitive loading forms a load pole. The break frequency follows from: where E.g. let RLOAD = ∞ and CLOAD = 1nF, then the load pole is located at 38.8kHz, giving rise and fall times of 8.8us. Sense Resistor Considerations The choice of value of the sense resistor entails a trade- off 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: 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 3mΩ at 500kHz. f = 2 π τ τ = ( ) • R R C B LOAD LOAD HV7800 ROUT = 3.3kΩ ± 30% ILOAD RSENSE CLOAD RLOAD IN LOAD GND OUT Sense Resistor

Supertex inc.

1235 Bordeaux Drive, Sunnyvale, CA 94089

TEL: (408) 222-8888 / FAX: (408) 222-4895 www.supertex.com ©2006 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited. 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. Doc.# DSFP - HV7800 NR031306 HV7800 Protection of the LOAD input In situations where the sense voltage can signifi cantly exceed 500mV, the LOAD input to the differential amplifi er should be protected by the addition of a protection resistor and two diodes as shown below: An excessive sense voltage might occur when line or load current is signifi cantly 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. HV7800 IN LOAD GND OUT RPROTECT RSENSE ISURGE Top View Front View Side View All dimensions are in millimeters Legend: min max 0.30 0.55 0.09 0.20 0.90 1.45 0.30 0.50 0.00 0.15 0.90 1.30 0.95ref 1.90ref 2.60 3.00 2.80 3.05 1.50 1.75 Pin 1 5-Lead SOT-23 (K1) Package Outline (The package drawing(s) in this data sheet may not refl ect the most current specifi cations. For the latest package outline informa- tion go to http://www.supertex.com/packaging.html.)