BTM7741G Datasheet, PDF (8/18 Pages) Infineon Technologies AG – TrilithIC

BTM7741G
4
Circuit Description
4.1
Input Circuit
The control inputs IH1,2 consist of TTL/CMOS compatible Schmitt-Triggers with hysteresis. Buffer amplifiers are
driven by these stages and convert the logic signal into the necessary form for driving the power output stages.
The inputs are protected by ESD clamp-diodes. The inputs IL1 and IL2 are connected to the internal gate-driving
units of the N-channel vertical power-MOS-FETs.
4.2
Output Stages
The output stages consist of an low R_DSON Power-MOS H-bridge. In H-bridge configuration, the D-MOS body
diodes can be used for freewheeling when communicating inductive loads. If the high-side switches are used as
single switches, positive and negative voltage spikes which occur when driving inductive loads are limited by
integrated power clamp diodes.
4.3
Short Circuit Protection
The outputs are protected against
– output short circuit to ground
– output short circuit to the supply voltage, and
– overload (load short circuit).
An internal OP-Amp controls the Drain-Source-Voltage by comparing the DS-Voltage-Drop with an internal
reference voltage. Above this trip point the OP-Amp reduces the output current depending on the junction
temperature and the drop voltage.
4.4
Overtemperature Protection
The high-side and the low-side switches also incorporate an over temperature protection circuit with hysteresis
which switches off the output transistors. In the case of the high-side switches, the status output is set to low.
4.5
Undervoltage Lockout
When V_S reaches the switch-on voltage V_UVON the IC becomes active with a hysteresis. The High-Side output
transistors are switched off if the supply voltage V_S drops below the switch off value V_UVOFF.
4.6
Open Load Detection
The open load detection of the BTM7741G works in OFF condition and is based on a voltage measurement at the
source of the high side switch. In order to use the open load detection SH2 has to be connected to Vcc via a pull
up resistor. Because this pull up resistor would connect the bridge output to the µC supply it needs to be
disconnected whenever the high side switch is on. This can be done by a transistor as shown in the application
example (Figure 4 “Application Example BTM7741G” on Page 15). To check for open load:
• Set IH1 = IH2 = LOW (both high side switches off)
• Set IL2 = LOW, IL1 = HIGH (only low side switch 1 is on)
• Connect Rol (open load pull up) to 5V via transistor
If the load is connected properly it will pull down the voltage at SH2 to a value close to 0V.
If the load is disconnected the resistor will pull the voltage at SH2 to value close to Vcc.
If the voltage at SH2 is higher than the open load detection voltage V_OUT(OL) then ST will be pulled down.
Data Sheet
8
Rev. 1.0, 2007-05-21