5.37 12-Bit ADC, External Reference
over recommended ranges of supply voltage and operating free-air temperature (unless otherwise noted)(1)
| PARAMETER |
TEST CONDITIONS |
VCC |
MIN |
MAX |
UNIT |
| VeREF+ |
Positive external reference voltage input |
VeREF+ > VREF–/VeREF–(2) |
|
1.4 |
AVCC |
V |
| VREF–/VeREF– |
Negative external reference voltage input |
VeREF+ > VREF–/VeREF–(3) |
|
0 |
1.2 |
V |
(VeREF+ –
VREF–/VeREF–) |
Differential external reference voltage input |
VeREF+ > VREF–/VeREF–(4) |
|
1.4 |
AVCC |
V |
| IVeREF+ |
Static input current |
0 V ≤ VeREF+ ≤ VAVCC |
2.2 V, 3 V |
|
±1 |
µA |
| IVREF–/VeREF– |
Static input current |
0 V ≤ VeREF– ≤ VAVCC |
2.2 V, 3 V |
|
±1 |
µA |
| CVREF+/- |
Capacitance at VREF+ or VREF- terminal |
(5) |
|
10 |
|
µF |
(1) The external reference is used during conversion to charge and discharge the capacitance array. The input capacitance, Ci, is also the dynamic load for an external reference during conversion. The dynamic impedance of the reference supply should follow the recommendations on analog-source impedance to allow the charge to settle for 12-bit accuracy.
(2) The accuracy limits the minimum positive external reference voltage. Lower reference voltage levels may be applied with reduced accuracy requirements.
(3) The accuracy limits the maximum negative external reference voltage. Higher reference voltage levels may be applied with reduced accuracy requirements.
(4) The accuracy limits minimum external differential reference voltage. Lower differential reference voltage levels may be applied with reduced accuracy requirements.
(5) Two decoupling capacitors, 10 µF and 100 nF, should be connected to VREF to decouple the dynamic current required for an external reference source if it is used for the ADC12_A. Also see the
MSP430F5xx and MSP430F6xx Family User's Guide.