U6815BM_09 Datasheet, PDF (6/14 Pages) ATMEL Corporation – Dual Hex DMOS Output Driver with Serial Input Control

4. Power Supply Fail
In the event of over or undervoltage at pin VS, an internal timer is started. When the overvoltage
delay time (t_dOV) programmed by the SCT Bit or the undervoltage delay time (t_dUV) is reached,
the power-supply fail bit (PSF) in the output register is set and all outputs are disabled. When
normal voltage is present again, the outputs are immediately enabled. The PSF bit remains high
until it is reset by the SRR bit in the input register.
5. Open-load Detection
If the open-load detection bit (OLD) is set to low, a pull-up current for each high-side switch and
a pull-down current for each low-side switch is turned on (open-load detection current I_HS1-6,
I_LS1-6). If V_VS – V_HS1-6 or V_LS1-6 is lower than the open-load detection threshold (open-load condi-
tion), the corresponding bit of the output in the output register is set to high. Switching on an
output stage with OLD bit set to low disables the open-load function for this output.
6. Overtemperature Protection
If the junction temperature exceeds the thermal prewarning threshold, T_{jPW set}, the temperature
prewarning bit (TP) in the output register is set. When temperature falls below the thermal pre-
warning threshold T_{jPW reset}, the bit TP is reset. The TP bit can be read without transferring a
complete 16-bit data word: with CS = high to low, the state of TP appears at Pin DO. After the
microcontroller has read this information, CS is set high and the data transfer is interrupted with-
out affecting the state of input and output registers.
If the junction temperature exceeds the thermal shutdown threshold T_{j switch off}, the outputs are
disabled and all bits in the output register are set high. The outputs can be enabled again when
the temperature falls below the thermal shutdown threshold, T_{j switch on}, and when a high has
been written to the SRR bit in the input register. Thermal prewarning and shutdown threshold
have hysteresis.
7. Short-circuit Protection
The output currents are limited by a current regulator. Current limitation takes place when the
over-current limitation and shutdown threshold (I_HS1-6, I_LS1-6) are reached. Simultaneously, an
internal timer is started. The shorted output is disabled during a permanent short when the delay
time (t_dSd) programmed by the Short-Circuit Timer (SCT) bit is reached. Additionally, the
Short-Circuit Detection (SCD) bit is set. If the temperature prewarning bit TP in the output regis-
ter is set during a short, the shorted output is disabled immediately and SCD bit is set. By writing
a high to the SRR bit in the input register, the SCD bit is reset and the disabled outputs are
enabled.
7.1 Inhibit
There are two ways to disable the U6815BM:
1. Set bit SI in the input register to zero
2. Switch Pin 17 (INH) to 0V
In both cases, all output stages are turned off but the serial interface stays active. The output
stages can be activated again by bit SI = 1 or by pin 17 (INH) switched back to 5V.
6 U6815BM
4545D–BCD–04/09