Datasheet

LM12L458
SNAS085B –JULY 1999–REVISED MARCH 2013 www.ti.com
Converter Characteristics
The following specifications apply for V
A
+ = V
D
+ = +3.3V, V
REF+
= +2.5V, V
REF−
= 0V, 12-bit + sign conversion mode, f
CLK
=
6.0 MHz, R
S
= 25Ω, source impedance for V
REF+
and V
REF−
≤ 25Ω, fully-differential input with fixed 1.25V common-mode
voltage, and minimum acquisition time unless otherwise specified. Boldface limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other
limits T
A
= T
J
= 25°C
(1)(2)(3)(4)
Symbol Parameter Conditions Typical
(5)
Limits
(6)
Units
ILE Integral Linearity Error After Auto-Cal
(7)(8)
±1/2 ±1 LSB (max)
TUE Total Unadjusted Error After Auto-Cal
(7)
±1 LSB
Resolution with No Missing Codes After Auto-Cal
(7)
13 Bits (max)
DNL Differential Non-Linearity After Auto-Cal ±1 LSB (max)
Zero Error After Auto-Cal
(9) (8)
±1/4 ±1 LSB (max)
Positive Full-Scale Error After Auto-Cal
(7)(8)
±1/2 ±3 LSB (max)
Negative Full-Scale Error After Auto-Cal
(7)(8)
±1/2 ±3 LSB (max)
DC Common Mode Error See
(10)
±2 ±4 LSB (max)
8-Bit + Sign and “Watchdog” Mode Integral
ILE See
(7)
±1/2 LSB (max)
Linearity Error
8-Bit + Sign and “Watchdog” Mode Total
TUE After Auto-Zero ±1/2 ±3/4 LSB (max)
Unadjusted Error
8-Bit + Sign and “Watchdog” Mode
9 Bits (max)
Resolution with No Missing Codes
8-Bit + Sign and “Watchdog” Mode
DNL ±1 LSB (max)
Differential Non-Linearity
8-Bit + Sign and “Watchdog” Mode Zero
After Auto-Zero ±1/2 LSB (max)
Error
8-Bit + Sign and “Watchdog” Full-Scale
±1/2 LSB (max)
Error
8-Bit + Sign and “Watchdog” Mode DC
±1/8 LSB
Common Mode Error
Multiplexer Channel-to-Channel Matching ±0.05 LSB
GND V (min)
V
IN+
Non-Inverting Input Range
V
A
+ V (max)
GND V (min)
V
IN−
Inverting Input Range
V
A
+ V (max)
−V
A
+
V (min)
V
IN+
− V
IN−
Differential Input Voltage Range
V
A
+ V (max)
GND V (min)
Common Mode Input Voltage Range
V
A
+ V (max)
(1) Two on-chip diodes are tied to each analog input through a series resistor, as shown below. Input voltage magnitude up to 5V above
V
A
+ or 5V below GND will not damage the LM12L458. However, errors in the A/D conversion can occur if these diodes are forward
biased by more than 100 mV. As an example, if V
A
+ is 3.0 V
DC
, full-scale input voltage must be =3.1 V
DC
to ensure accurate
conversions. See Figure 3
(2) V
A
+ and V
D
+ must be connected together to the same power supply voltage and bypassed with separate capacitors at each V
+
pin to
assure conversion/comparison accuracy.
(3) Accuracy is ensured when operating at f
CLK
= 6 MHz.
(4) With the test condition for V
REF
= V
REF+
- V
REF-
given as +2.5V, the 12-bit LSB is 305 µV and the 8-bit/“Watchdog” LSB is 4.88 mV.
(5) Typical figures are at T
A
= 25°C and represent most likely parametric norm.
(6) Limits are specified to AOQL (Average Output Quality Level).
(7) Positive integral linearity error is defined as the deviation of the analog value, expressed in LSBs, from the straight line that passes
through positive full-scale and zero. For negative integral linearity error the straight line passes through negative full-scale and zero.
(See Figure 10 and Figure 11).
(8) The LM12L458's self-calibration technique ensures linearity and offset errors as specified, but noise inherent in the self-calibration
process will result in a repeatability uncertainty of ±0.10 LSB.
(9) Zero error is a measure of the deviation from the mid-scale voltage (a code of zero), expressed in LSB. It is the worst-case value of the
code transitions between -1 to 0 and 0 to +1 (see Figure 12).
(10) The DC common-mode error is measured with both inputs shorted together and driven from 0V to +2.5V. The measured value is
referred to the resulting output value when the inputs are driven with a 1.25V signal.
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