Microchip HV257DB2 Manual

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Supertex inc.

www.supertex.com

HV257DB2

Doc.# DSDB-HV257DB1

B032114

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, VPP

, and four low voltage supplies, AVDD and DVDD,

AVNN and DVNN, are required. Referring to the demo board

drawing shown below, the logic and VSIG 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.

High Voltage Sample and Hold Amplier Array

Specications

Parameter Value

VPP

, High voltage supply: 300V

AVDD / DVDD, Low voltage positive supply 6.0 to 7.5V:

AVNN / DVNN, Low voltage negative supply -4.5 to -6.5V:

VSIG, Input signal range 0 to 5.0V:

HVOUT, Output voltage swing 0 to 295V

, Closed loop gain 72V/V ±5%

SR, Output slew rate into 100pF load 2.0V/µs

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 VPP and AVDD. Any low current high voltage diode can

be used. The second diode can be any low voltage schottky

diode across AVNN and GND.

Acceptable Power Up Sequences

1) VPP 2) VNN 3) VDD 4) Inputs & Anode

1) VNN

2) VDD 3) VPP 4) Inputs & Anode

Acceptable Power Down Sequences

1) Inputs & Anode 2) VDD 3) VNN 4) VPP

1) Inputs & Anode 2) VPP 3) VDD 4) VNN

Inputs and Outputs

The output of the HV257FG will swing from 0 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 VSIG. 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

24.9kΩ for ±500µA 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.

HV257DB2

DGND

DVDD

DVNN

AGND

No Connect

AVDD

AVNN

VPP

VSIG

VSGND

HVOUT0

HVOUT31

HV257

pin1

R1 R2

C10

Supertex inc.

Board Layout and Connections

Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives

an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability

to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and

specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com)