HV257DB2 general description the supertex HV257DB2 is a 32-channel, 295v, sample and hold ampli? er array with a nominal gain of 72v/v. the purpose of the HV257DB2 is to provide a means to easily evaluate the supertex hv257fg device. a high voltage supply, v pp , and four low voltage supplies, av dd and dv dd , av nn and dv nn , are required. referring to the demo board drawing shown below, the logic and v sig connections are on the left, the high voltage outputs are on the bottom, and the supplies are on the right. please follow the power up/down sequence to avoid damaging the device. board layout high voltage sample and hold array speci? cations parameter value v pp , high voltage supply: 300v av dd / dv dd , low voltage positive supply: 6.0v to 7.5v av nn / dv nn , low voltage negative supply: -4.5v to -6.5v v sig , input signal range: 0v to 5.0v hv out , output voltage swing 0v to 295v a v , closed loop gain 72v/v 5% sr, output slew rate into 100pf load 2.0v/s power up/down sequence the device can be damaged due to improper power up/down sequence. to prevent damage, please follow the acceptable power up/down sequences. two external diodes, d1 and d2, are added in the demo board to prevent damage dur- ing power up/down. the ? rst diode is a high voltage diode across v pp and v dd . any low current high voltage diode can be used. the second diode can be any low voltage schottky diode across v nn and gnd. acceptable power up sequences 1) v pp 2) v nn 3) v dd 4) inputs & anode or 1) v nn 2) v dd 3) v pp 4) inputs & anode acceptable power down sequences 1) inputs & anode 2) v dd 3) v nn 4) v pp or 1) inputs & anode 2) v pp 3) v dd 4) v nn HV257DB2 dgnd dv dd dv nn agnd no connect av dd av nn av pp en a0 a1 a2 a3 a4 v sig v sgnd hv out 0 hv out 31 pin1 c1 c2 c3 c4 c5 d1 d2 c6 c7 c8 c9 r1 r2 r3 c10 u1 hv257
2 HV257DB2 bill of materials circuit diagram nr041207 inputs and outputs the output of the hv257fg will swing from 0v to 295v. the internal closed loop gain is set at 72v/v. an input voltage of 4.096v will give an output of 295v. input voltages of up to 5.0v can be applied but will cause the ampli? er to saturate. when en is high, the addressed output, determined by a0 to a4, will be sampling the input signal v sig . when en is low, all the internal sampling switches are open. the output current source and sink for all 32 channels can be adjusted using r1 and r2. the limit is approximately 12.5v divided by the resistor value. the demo board uses 24.9k for 500a limiting. temperature diode the hv257fg has an integrated silicon diode to help moni- tor the die temperature if desired. pin 95 is the anode and pin 96 is the cathode. pads are available on the board for these connections. hv out 0 v sig a0 a1 a2 a3 en a4 r source r sink dv dd av nn agnd dgnd v pp av dd dv nn byp-v pp byp-av dd byp-av nn anode cathode r2 24.9k ? r1 24.9k ? c6 0.1f c8 0.1f c7 0.1f hv out 1 hv out 2 hv out 31 hv out 30 hv257fg c1 10nf c2 0.1f c3 0.1f logic control inputs analog input high voltage outputs v pp av nn av dd d2 d1 c4 0.1f c5 0.1f dv nn dv dd + - 43, 89 agnd 39 r3 0 ? c9 0.1f c10 0.1f agnd dgnd description value package manufacturer part number c1 x7r chip capacitor 500v, 0.01f10% 0805 tecate cmc-500103kx0805t c2-c9 x7r chip capacitor 25v, 0.1f10% 0805 tecate cmc-025104kx0805t c10 x7r chip capacitor 10v, 1.0f10% 0805 any --- r1 chip resistor 24.9k, 1% 0805 any --- r2 chip resistor 24.9k, 1% 0805 any --- r3 chip resistor 0 0805 any --- d1 recti? er diode 400v, 1.0a sma diodes inc us1g d2 schottky diode 20v, 20ma sod-323 diodes inc sd103cws u1 ampli? er array 300v 100-lead mqfp supertex hv257fg
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