DRV8432: DRV8432 in parallel full bridge mode to drive Peltier Module for heating and cooling - using EVAL8432 and own design

Part Number:DRV8432

Hi,

I'm using DRV8432-EVAL module in PFB(parallel Full Bridge) Mode to drive Peltier module rating 24V/12A.

I have worked on My own designed DRV8432 PCB in PFB mode. myschematic design also attached here.

The board is working good PVDD=12V driving 4A current.(Please visit the site to view this file)

if voltage is changed to PVDD=15V trying to drive 6A current and IC 8432 and heat sink are getting too hot and  finally driving 1.8A of current showing  5V(30% DC) on output though the PWM is 98% (DC).

Mode: PFB

PWM Freq : 40Khz

1 . Peltier - heating 

PWMA - 98% Duty Cycle

PWMB -1% DC

2.  Peltier - cooling

PWMA -1% DC

PWMB - 98% Duty Cycle

Why cause this? How to solve this problem?

Thanks 

Regards

Sai