Circuitry for a high voltage linear current sense IC

Abstract

A high voltage linear current sense integrated circuit includes a differential amplifier circuit that can amplify a differential signal in the hundreds of millivolts near the power supply. In addition, a constant current using opposing minus temperature coefficient MOSFETs is provided. Accordingly, an op-amp circuit is provided with an input offset voltage which is constant and insensitive to temperature changes. A circuit for generating a current reference on the high side of the current sense IC also is provided.

1. A current sense integrated circuit, comprising:
 an amplifier circuit for receiving and amplifying a differential analog input signal at a first voltage level containing current sense information, wherein the amplifier circuit includes a circuit to minimize inherent offset voltage temperature offset  drift, comprising a first pair of mirrored MOSFET's, such that the circuit has an offset voltage which is equal to the difference between the respective gate-to-source voltages of the MOSFET's and remains constant over temperature variations;  
 a pulse width modulator circuit for converting the differential analog input signal to a pulse width modulated signal at the first voltage level; and  
 a level shift circuit for converting the pulse width modulated signal from the first voltage level to a second voltage level; and  
 a recovery circuit for reconstructing the analog input signal at the second voltage level. . 
 
     
     
       2. The current sense integrated circuit of  claim 1 , wherein the circuit to minimize inherent temperature offset drift comprises a pair of mirrored MOSFETs, such that the circuit has an offset voltage which is equal to the difference between the gate-to-source voltage of the MOSFETs and remains constant over temperature variations. 
     
     
       3. The current sense integrated circuit of  claim 1 , wherein the level shift circuit comprises a pulse generator circuit for producing rising edge triggered pulses and falling edge triggered pulses from the pulse width modulated signal and a pair of MOSFETs for receiving the rising edge triggered pulses and the falling edge triggered pulses and transposing those pulses from the first voltage level to the second voltage level. 
     
     
       4. The current sense integrated circuit of  claim 1 , further comprising a high side current reference circuit. 
     
     
       5. The current sense integrated circuit of  claim 1 , wherein said first pair of mirrored MOSFET's receive said differential analog input signal.  
     
     
       6. The current sense integrated circuit of  claim 1 , further comprising a second pair of mirrored MOSFET's connected respectively in series with said first pair of mirrored MOSFET's for equalizing current and biasing of said first pair.  
     
     
       7. A current sense integrated circuit as claimed in  claim 1 , wherein said amplifier circuit has a differential input stage for receiving said differential analog input signal, said differential input stage having two branches including inverting and non- inverting inputs, respectively, and said first pair of mirrored MOSFET's being connected in said two branches, respectively.    
     
     
       8. A current sense integrated circuit as claimed in  claim 7 , further comprising an output stage of said amplifier circuit, and a further matched pair of MOSFET's respectively connected for controlling current in said input stage and said output stage.