VNH5019 drive capability evaluation

[horace zhu]

Posted on March 06, 2018 at 05:01

hi , i am going to use the VNH5019 driver to drive continuous 10 A  for motor load, 

can the driver have the capability? how to calculate the thermal analysis?

thanks

#brushed-motor-driver #vnh5019

[leonardo miccoli]

Posted on March 08, 2018 at 11:38

Hi Horace,

Thermal performance for H-Bridge depends on several factor: Load profile, initial temperature, supply Voltage, PWM frequency, pcb layout. VNH5019AY Thermal Performance  is described in the Datasheet, Chapter 3.

Here is an example on how to

calculate thermal analysis  based on

your request: ILoad=10A continuous.

The power that VNH5019AY will manage is, (fixing max RDSonHS=0.0265Ohm, Max RDSonLS=0.0265Ohm):

PHS= RDSonHS * ILoad * ILoad = 2.65W;

PLS= RDSonLS * ILoad * ILoad = 1.15W;

Assuming a pcb with 16 cm2 Cu heat sink area (refer to fig18 @ page26 in the Datasheet):

RTH_HS=26°C/W; RTH_LS=31°C/W ; RTH_HL=18°C/W ; RTH_LL=15°C/W.

It will lead to a Delta Tj:

DTjH=

PHS*

RTH_HS+ PLS*

RTH_HL=89.6°C;

DTjL=

PLS*

RTH_LS+ PLS*

RTH_HL=83.35°C;

Starting from a Tamb=25°C max Tj will be 114.6°C, that is under thermal protection value (min 150°C).

This consideration can be performed starting from different ambient temperature, load profile, PWM switching frequency, pcb layout.

If you want to perform further analysis with different condition, I suggest you to download TwisterSIM: a unique electro-thermal simulator that helps shorten the design solution cycle by enabling complex engineering evaluations.

TwisterSIM is available for free at

http://www.st.com/twistersim%20and%20include%20all%20M05

 it include thermal model for all VIPowerâ„¢ M0-5 & M0-7 H-bridge family.

Thanks and Regards,

Leonardo

[horace zhu]

Posted on March 09, 2018 at 07:43

hello  leonardo,

Really thanks for your reply.

16 cm^2 heat sink is really big. it should be not that much in actual design.Per your calculation,it can't work in 85C operation temperature.but I have to say,your calculation process is a little difference with Table 17 page27.

following picture is load work current curve in a cycle.

the total work time in a cycle  is about 7ms. peak current @8~9A. PWM frequency is 10Khz.

total PCB heat sink for CHIP1,CHIP2,CHIP3 is 4CM^2  .could you give a more detail analysis?

by the way,the transient thermal analyis is really tough. could you have a good method?

[horace zhu]

Posted on March 19, 2018 at 02:20

hi leonardo,

I want to use it to control external NMOSFET for anti reversal connection for the whole load

the load including other HSD and full bridge driver. 

this make use of VNH5019 itself provide charge pump function,

is it possible with only VNH5019 to realize all loads anti reverse conncetion protection?

looking forward  to your reply

[leonardo miccoli]

Posted on March 22, 2018 at 10:18

Hi Horace,

For detailed thermal simulation my suggestion is to use the

TwisterSIM available for free at

/external-link.jspa?url=http%3A%2F%2Fwww.st.com%2Ftwistersim%2520and%2520include%2520all%2520M05

.

Ithasa graphical interface and it's a easy way to perform accurate thermal simulation especially in transient condition.

For example I performed the case you requested: VNH5019 with a Load=9A,

mailto:PWM@10KHz

(50% DC) 7ms cycle Tamb=85°C. Here attached the relatedplot:

As you can see no issue to drive this load.

Regarding your request

using internal charge pump

to drive NMOSFET for anti reversal connection for the whole load :

In reverse battery conditionthere isno issue. In direct connection it is possible but it is mandatory to proper dimension the NMOSET able to drive the current for the whole load (VNH5019+ other HSD+ full bridge driver )@ max load condition.

Thanks for your interest inVI Power H-Bridgefamily and Best Regards,

Leonardo

[horace zhu]

Posted on April 25, 2018 at 11:16

sorry, I can't get the analysis tool,could you help check if it is available now?