This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. Send mail to mime@docserver.cac.washington.edu for more info. ---1463811840-1070400604-1030171901=:1354 Content-Type: TEXT/PLAIN; charset=US-ASCII Not code, but try this clamp circuit (attached). It has worked for me with chips whose A/D converter suffers when the substrate clamp diodes are active. Set Rx for 500uA to 1mA through the current mirrors. This will clamp up to 50mA with negligible excursion over/under Vcc/GND using common transistors (2N3904/3906 BC55x 2SC1815 etc). Peter ---1463811840-1070400604-1030171901=:1354 Content-Type: APPLICATION/PDF; name="clamp.pdf" Content-Transfer-Encoding: BASE64 Content-ID: Content-Description: clamp.pdf Content-Disposition: attachment; filename="clamp.pdf" JVBERi0xLjIKJcfsj6IKNCAwIG9iago8PC9MZW5ndGggNSAwIFIvRmlsdGVy IC9GbGF0ZURlY29kZT4+CnN0cmVhbQp4nHVXy64cRQzd91f0MoBS2K73Ei4I CRFEwogfmChS0J1FVuTzY7ve1YPuYq5dx67jUy53Nxg8Qf7q7/1xfDnw/Hxk E/353xHOd2z+fqBPZPyJFKwsPA4Mbna8Hn93F6QN49wFY10wpJhEF0x1eWh5 nmBqHky45qmbz3mAtjwzJmIwPnIiBENRQNEn44g9EE0MJ8aQDAaxyaA9tyR3 DojZOGQAoQkkAdkESUnRkGPb1S0CGbIa4dAkibCZl60zVsNls5XO/fj0/aE7 L9rDVXvYtYer9rBpn8IOqZ6u/BXRknThK2TStHloTTIhMkvqrJ1Uz8R1p6F6 Zh2SqFNVX3Pcjwye8bmLntEba6mLnm3boYmeuQZMsYiePZigBou+symiZ62T XBOdAGaHlNFclDZMcBeMb6ITpgumumKT/Rmm5rFN94ahdMlDtOWZMRClWs5N zkSrpL1oxxQTX3p3EjjWNovtDNK5VXCXAD4cBvrgTOBACHJ4bEfWL5zEx6Rb +EgmRo3IrLemTJJKjhHZDIBqrpTmph/618ab9W8u2pp+1q25/Nr0M6R64tr0 z5LYtelnXZtnbfoZkUUlngtD+cyCh5C68jnLIMGu/MadezjJKMKufBbhcCif bd2iK5+9DBfblM9BBo9tyu+UivKXUb/On7kb3YaZT6de2ZzTogjCjoi0IPjG /n8OBLaiyvF68KVny2KxdC2leS25eS3meS36trawmM4St4agC699Tl6YU9r6 Ie7V5y0FjBQ8qMu87s8vu8395uj7XnlUyHRS1dHP4XoudWzEPtaKnRtimzOj mB6x1FZohJWEmnyQ3L1ouUkzN6Urh9cpp9r2aC0YiBOAYIpWI7SncTH5cOVp 0ANLI/TMxRR027oBlFeLnjjr1UhpaQu1UFmkyHl09pFSbKJSLSF5IeLGuoMR q/9D3UYtyMqgR0EZPDVrtRjbdm3rwqjFTlw7+dYZj2rZhTy/VE3kmzXI93Wm 2GP1f5rI84BayKPMmikrbOT7ujLCTn5klaEkZzGNpGKu/YO09E8zR/8MAPfI iFZj6R+ktX+Qlv5p5uifAVBeU/+MzHIE21Co75LN8bq/+pbLSE+uVrw89afb Ss8R0/uFo3UaVceYPtu7s2aJ5bmQwpqlORTj3IpQswhNzhat6ozu4e2YWMOi dgcATNFqNDGrWYQegeUUeuZ2TGPrBlBeLXriXJtNj9nCPjMTbQNtnGQx7TrQ klsGWnL7QOsAGVo9Wg1aBlrCdaAlWAZagn2gdYDywmmgJbpUGmAt1LdXn2pP vaQ5eq8Vi5+rKF9Kde8Ec9XVGkX3Za5rhIqR5pJjFM6ulxzDXHG1RsF9WQj1 0MFVy/3CDa2fufXn/jh/vh0/fghn5Jy3T0f5COYXrOANf1xkMpZjb483L3/8 9O6v727/Hm+RvyxAdmKOt49vfvjn5UX8oM63fKXE+9ufvyg4gLHy+SS+D1/F 9evtfH+8P74BoVH7zWVuZHN0cmVhbQplbmRvYmoKNSAwIG9iagoxMTE1CmVu ZG9iagozIDAgb2JqCjw8Ci9UeXBlIC9QYWdlCi9NZWRpYUJveCBbMCAwIDQw MCA0MDBdCi9QYXJlbnQgMiAwIFIKL1Jlc291cmNlcyA8PCAvUHJvY1NldCBb L1BERiAvVGV4dF0KL0ZvbnQgPDwKL1I2IDYgMCBSCj4+Cj4+Ci9Db250ZW50 cyA0IDAgUgo+PgplbmRvYmoKNiAwIG9iago8PC9UeXBlL0ZvbnQvTmFtZS9S Ni9TdWJ0eXBlL1R5cGUxL0Jhc2VGb250L0hlbHZldGljYT4+CmVuZG9iagoy IDAgb2JqCjw8IC9UeXBlIC9QYWdlcyAvS2lkcyBbCjMgMCBSCl0gL0NvdW50 IDEKPj4KZW5kb2JqCjEgMCBvYmoKPDwgL1R5cGUgL0NhdGFsb2cgL1BhZ2Vz IDIgMCBSCj4+CmVuZG9iago3IDAgb2JqCjw8IC9DcmVhdGlvbkRhdGUgKEQ6 MjAwMjA4MjQwOTQ1MDgpCi9Qcm9kdWNlciAoR05VIEdob3N0c2NyaXB0IDUu MTApCj4+CmVuZG9iagp4cmVmCjAgOAowMDAwMDAwMDAwIDY1NTM1IGYgCjAw MDAwMDE0OTggMDAwMDAgbiAKMDAwMDAwMTQzOSAwMDAwMCBuIAowMDAwMDAx MjIwIDAwMDAwIG4gCjAwMDAwMDAwMTUgMDAwMDAgbiAKMDAwMDAwMTIwMCAw MDAwMCBuIAowMDAwMDAxMzY4IDAwMDAwIG4gCjAwMDAwMDE1NDcgMDAwMDAg biAKdHJhaWxlcgo8PCAvU2l6ZSA4IC9Sb290IDEgMCBSIC9JbmZvIDcgMCBS Cj4+CnN0YXJ0eHJlZgoxNjM0CiUlRU9GCg== ---1463811840-1070400604-1030171901=:1354-- -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu