Create a program that simulates a simple ATM. The program should prompt the user to enter a PIN. If the correct PIN is entered, the program should display a menu with options to check balance, deposit, or withdraw money. Perform the respective actions based on the user's choice.

Input (PIN): 1234

Output: 

Welcome to Simple ATM!

Menu:

1. Check Balance

2. Deposit Money

3. Withdraw Money

Enter your choice (1/2/3): 2

Enter the amount to deposit: 500

New balance: $500

Enter your choice (1/2/3): 1

Output: Your current balance is $500.