Posted on April 23, 2015 at 09:46Hi, Arya,
Basically the THSD pin shouldn't be involved during the power up/down sequence. Normally the user should force THSD thru 10KΩ [pull-up resistor] at VDDP/DVDS in order to set properly the thermal shutdown circuitry. If the internal temperature surpasses 153 °C, THSD goes down and all
STHV748 channels are in HZ state.
It’s not forbidden to connect THSD direct to DVDD/VDDP but
first off you have to respect to rise up VDDP/DVDD
before VDDM, inasmuch you can generate conflict into cmos logic embedded and it can be visible anomalous
current absorption from LV supply. The other side effect connecting THSD directly to VDDP/DVDD is the thermal shutdown circuitry disabled, than the user cannot safe control the pulser on a rise temperature over limit..
THSD is global pin when it being pushed to “0� the outputs pulser go in high impedance resetting
the logic, than it is safe to manage it independently from power-up/down sequence.
Regards
Antonio
[
mailto:antonio.ricciardo@st.com
Technical Marketing TME @STMicro]
Hi
Is there any particular sequence of giving the THSD voltage? We initially had connected it to high voltage directly without giving the pull up resistor. The chip works fine when VDDM is given first and VDDP (also DVDD) given second. But it draws infinite current when VDDP is connected first and VDDM is given afterwards. We removed THSD pin and manually connected it to positive supply after giving the power supplies and the IC works fine irrespective of the order of the supplies. How is this possible?
