Datasheet

LM12454, LM12458, LM12H458
www.ti.com SNAS079A –MAY 2004–REVISED FEBRUARY 2006
CONVERTER CHARACTERISTICS
(1) (2) (3) (4)
The following specifications apply to the LM12454, LM12458, and LM12H458 for V
A
+ = V
D
+ = 5V, V
REF+
= 5V, V
REF−
= 0V, 12-
bit + sign conversion mode, f
CLK
= 8.0 MHz (LM12H458) or f
CLK
= 5.0 MHz (LM12454/8), R
S
= 25Ω, source impedance for
V
REF+
and V
REF−
≤ 25Ω, fully-differential input with fixed 2.5V 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.
Symbol Parameter Conditions Typical
(5)
Limits
(6)
Units
ILE Integral Linearity Error
(7) (8)
After Auto-Cal ±1/2 ±1 LSB (max)
TUE Total Unadjusted Error
(7)
After Auto-Cal ±1 LSB
Resolution with No Missing Codes
(7)
After Auto-Cal 13 Bits (max)
DNL Differential Non-Linearity After Auto-Cal ±¾ LSB (max)
After Auto-Cal ±1
Zero Error
(9) (8)
LM12H458 ±1/2 ±1.5 LSB (max)
Positive Full-Scale Error
(7) (8)
After Auto-Cal ±1/2 ±2 LSB (max)
Negative Full-Scale Error
(7) (8)
After Auto-Cal ±1/2 ±2 LSB (max)
DC Common Mode Error
(10)
±2 ±3.5 LSB (max)
8-Bit + Sign and “Watchdog” Mode
ILE ±1/2 LSB (max)
Integral Linearity Error
(7)
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 Resolution
9 Bits (max)
with No Missing Codes
8-Bit + Sign and “Watchdog” Mode
DNL ±3/4 LSB (max)
Differential Non-Linearity
8-Bit + Sign and “Watchdog” Mode Zero Error After Auto-Zero ±1/2 LSB (max)
8-Bit + Sign and “Watchdog” Full-Scale Error ±1/2 LSB (max)
8-Bit + Sign and “Watchdog” Mode
±1/8 LSB
DC 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)
V (min)
GND
V (max)
Common Mode Input Voltage Range
V
A
+
(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 LM12454 or the LM12(H)458. 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 4.5 V
DC
, full-scale input voltage must be ≤4.6 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
= 5 MHz for the LM12454/8 and f
CLK
= 8 MHz for the LM12H458.
(4) With the test condition for V
REF
(V
REF+
− V
REF−
) given as +5V, the 12-bit LSB is 1.22 mV and the 8-bit/“Watchdog” LSB is 19.53 mV.
(5) Typical figures are at T
A
= 25°C and represent most likely parametric norm.
(6) Limits are 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 5 Figure 6).
(8) The LM12(H)454/8'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 7).
(10) The DC common-mode error is measured with both inputs shorted together and driven from 0V to 5V. The measured value is referred to
the resulting output value when the inputs are driven with a 2.5V signal.
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