Microchip Technology MCP651, Руководство пользователя

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Installation and Operation
©
2009 Microchip Technology Inc. DS51834A-page 13
6. Voltmeter to measure VOUTX
a) Typically not used (mainly used for validating DUT and board).
7. POT (RCAL) Thumb-wheel (to adjust VCALX)
a) Rotate clockwise (CW) to increase VCALX.
b) Rotate counter-clockwise (CCW) to decrease VCALX.
c) Usually set at mid-turn.
d) Can override with an external power supply at VCALX or a jumper wire (see
# 9 below)
8. Power Supply for VSSX
a) Minimum of about VDDX – (DUT’s maximum operating supply
voltage) – (0.12V for the resistors in the supply line).
b) Maximum of +0.3V (for V
CMX
at 0.3V below negative rail).
c) When VSSX = -2.5V and VDDX = +2.5V, you can connect to the -2.5V
supply with a jumper wire (fewer lab power supplies).
9. Power Supply for VCALX
a) Usually not connected (RCAL sets V
CALX
; fewer lab power supplies).
b) Can be shorted to GND with a jumper wire (fewer lab power supplies;
V
CALX
= V
CMX
= 0V).
c) Can connect to an external lab power supply (it is best, but not necessary, to
set RCAL to mid-supply).
10. Power Supply for VDDX
a) Minimum of -0.3V (for V
CMX
at 0.3V above positive rail).
b) Maximum of about VSSX + (DUT’s maximum operating supply
voltage) + (0.12V for the resistors in the supply line).
c) When VSSX = -2.5V and VDDX = +2.5V, you can connect to the +2.5V
supply with a jumper wire (fewer lab power supplies).
11. CAL Switch
a) Press to initiate calibration sequence (corrects DUT’s V
OST
, with internal
common mode voltage set to VCALX).
b) There is a delay of about 4 ms for the calibration to complete, plus several
tenths of a second for the circuit to settle.
12. Voltmeter at VDDI and VDDX (to measure I
DD
)
a) Measure
Δ
V = V
DDX
– V
DDI
.
b) Calculate I
DD
=
Δ
V / (10
Ω
)
13. Voltmeter at VSSI and VSSX (to measure I
SS
)
a) Measure
Δ
V = V
SSX
– V
SSI
.
b) Calculate I
SS
=
Δ
V / (10
Ω
); (this is a negative value)
Note: For the best accuracy and ease of use, short VCALX to GND, set the other
voltages for the desired bias during calibration, then initiate a calibration
event in the DUT (push S1). Change the bias point afterwards to see how
V
OST
is changed.