My cash account is going negative after passing entries for cash deposited to bank.

It has some reason:

1- you have not enough cash balance. example: suppose you have Rs. 50000/- cash balance but you take Rs. 100000/- of cash deposited into bank entry. So here there is deficit of Rs. 50000/-, so your balance shows Cash A/c Rs. 50000 Cr.

2- It,s may be your cash account group selection is wrong it means your cash account belongs to Current Assets and it,s nature is always debit. but unfortunately you select wrong group at the time creation of Cash ledger. Example: Suppose you create cash A/c under current liability instead of current assets, so there is a chance of showing cash a/c credit balance.