MAX253 Transformer Driver for Isolated RS-485 Interface Pin ConfigurationPin DescriptionPINNAMEFUNCTION TOP VIEW 1 D1 Open drain of N-channel transformer drive 1. Ground. Connect both GND1 and GND2 2 GND1 to ground. Frequency switch. If FS = VCC or open, + 3 FS switch frequency = 350kHz; if V D1 FS = 0V, 1 8 D2 switch frequency = 200kHz. GND1 2 7 GND2 Shutdown. Ground for normal operation, MAX253 4 SD FS 3 connect high for shutdown. 6 VCC SD 4 5 N.C. Not internally connected. 5 N.C. 6 VCC 5V supply voltage. DIP/SO/ μ MAX Ground. Connect both GND1 and GND2 7 GND2 to ground. 8 D2 Open drain of N-channel transformer drive 2. www.maximintegrated.com Maxim Integrated | 5