VN771P

The VN771P is a device formed by three monolithic chips housed in a standard SO28 package: a double high side and two low side switches. Both the double high side and low side switches are made using STMicroelectronics VIPower technology. This VN771P device is suitable to drive a DC motor in a bridge configuration as well as to be used as a quad switch for any low voltage application. The dual high side switches have built-in thermal shut-down to protect the  VN771P chip from over temperature and short circuit,status output to provide indication for open load in off and on state, overtemperature conditions and stuck-on to VCC. The low side switches are two OMNIFET types (fully autoprotected Power MOSFET in VIPower] technology). They have built-in thermal shut-down, linear current limitation and overvoltage clamping. Fault feedback for hermal intervention can be detected by monitoring the voltage at the input pin.

DUAL HIGH-SIDE SWITCH From the falling edge of the input signal of VN771P, the status output, initially low to signal a fault condition (overtemperature or open load on-state), will go back to a high state with a different delay in case of overtemperature (tpovl) and in case of open open load (tpol) respectively.This feature allows to discriminate the nature of the detected fault. To protect the device against short circuit and over current condition, the thermal protection turns the integrated Power MOS off at a minimum junction temperature of 140 oC. When this temperature returns to 125 oC the switch is automatically turned on again. In short circuit the protection reacts with virtually no delay, the sensor (one for each channel) being located inside each of the two Power MOS areas. This positioning allows the device to operate with one channel in automatic thermal cycling and the other one on a normal load. An internal function of the devices ensures the fast demagnetization of inductive loads with a typical voltage (Vdemag) of -18V. This function allows to greatly reduces the power dissipation according to the formula:P_dem =0.5• Lload • (Iload)² • [(V_CC+V_demag)/V_demag] • f where f = switching frequency and Vdemag = demagnetization voltage.In this device if the GND pin is disconnected,with V_CC not exceeding 16V, both channel will switch off.

LOW-SIDE SWITCHES During normal operation, the Input pin of VN771P is electrically connected to the gate of the internal power MOSFET. The device then behaves like a standard power MOSFET and can be used as a switch from DC to 50 KHz. The only difference from the user's standpoint is that a small DC current (I_iss) flows into the Input pin in order to supply the internal circuitry.