Thanks for the reply. I found that some of the pins which were not supposed to be connected to the ground, were falsely connected to the ground. With the previous experience, I have found that the chip works fine when not soldered on the board, that is, the chip generates some voltages at the pwm pins when Vin is supplied. However, when the chip is soldered to the board, some of its pins are shorted to the ground.
So, I have ordered new chips and will solder the chip again. Accordingly, I will check the voltages at various pins of the chip.