Datasheet

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  
SLAS491A − AUGUST 2005 − REVISED OCTOBER 2005
40
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MSP430x20x2 electrical characteristics over recommended ranges of supply voltage and
operating free-air temperature (unless otherwise noted) (continued)
10-bit ADC, external reference (see Note 1, MSP430x20x2 only)
PARAMETER TEST CONDITIONS VCC MIN TYP MAX UNIT
V
eREF+
Positive external reference input
V
eREF+
> V
eREF−
SREF1 = 1, SREF0 = 0
1.4 V
CC
V
V
eREF+
Positive external reference input
voltage range (see Note 2)
V
eREF−
≤ V
eREF+
≤ V
CC
− 0.15V
SREF1 = 1, SREF0 = 1 (see Note 3)
1.4 3.0 V
V
eREF−
Negative external reference input
voltage range (see Note 4)
V
eREF+
> V
eREF−
0 1.2 V
∆V
eREF
Differential external reference input
voltage range
∆V
eREF
= V
eREF+
− V
eREF−
V
eREF+
> V
eREF−
(see Note 5) 1.4 V
CC
V
I
VeREF+
Static input current into V
eREF+
0V ≤ V
eREF+
≤ V
CC
,
SREF1 = 1, SREF0 = 0
2.2 V/3 V ±1 µA
I
VeREF+
Static input current into V
eREF+
0V ≤V
eREF+
≤ V
CC
− 0.15V ≤ 3V
SREF1 = 1, SREF0 = 1 (see Note 3)
2.2 V/3 V 0 µA
I
VeREF−
Static input current into V
eREF−
0V ≤ V
eREF−
≤ V
CC
2.2 V/3 V ±1 µA
NOTES: 1. The external reference is used during conversion to charge and discharge the capacitance array. The input capacitance, C
I
, 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 10-bit accuracy.
2. The accuracy limits the minimum positive external reference voltage. Lower reference voltage levels may be applied with reduced
accuracy requirements.
3. Under this condition the external reference is internally buffered. The reference buffer is active and requires the reference buffer
supply current I
REFB
. The current consumption can be limited to the sample and conversion period with REBURST = 1.
4. The accuracy limits the maximum negative external reference voltage. Higher reference voltage levels may be applied with reduced
accuracy requirements.
5. The accuracy limits the minimum external differential reference voltage. Lower differential reference voltage levels may be applied
with reduced accuracy requirements.