Datasheet

3
LTC1966
sn1966 1966fas
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
DD
= 5V, V
SS
= –5V, V
OUTRTN
= 0V, C
AVE
= 10µF, V
IN
= 200mV
RMS
,
V
ENABLE
= 0.5V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The inputs (IN1, IN2) are protected by shunt diodes to V
SS
and
V
DD
. If the inputs are driven beyond the rails, the current should be limited
to less than 10mA.
Note 3: The LTC1966 output (V
OUT
) is high impedance and can be
overdriven, either sinking or sourcing current, to the limits stated.
Note 4: The LTC1966C/LTC1966I are guaranteed functional over the
operating temperature range of –40°C to 85°C.
Note 5: The LTC1966C is guaranteed to meet specified performance from
0°C to 70°C. The LTC1966C is designed, characterized and expected to
meet specified performance from –40°C to 85°C but is not tested nor QA
sampled at these temperatures. The LTC1966I is guaranteed to meet
specified performance from –40°C to 85°C.
Note 6: High speed automatic testing cannot be performed with
C
AVE
= 10µF. The LTC1966 is 100% tested with C
AVE
= 22nF. Correlation
tests have shown that the performance limits above can be guaranteed
with the additional testing being performed to guarantee proper operation
of all the internal circuitry.
Note 7: High speed automatic testing cannot be performed with 60Hz
inputs. The LTC1966 is 100% tested with DC and 10kHz input signals.
Measurements with DC inputs from 50mV to 350mV are used to calculate
the four parameters: G
ERR
, V
OOS
, V
IOS
and linearity error. Correlation tests
have shown that the performance limits above can be guaranteed with the
additional testing being performed to guarantee proper operation of all
internal circuitry.
Note 8: The LTC1966 is inherently very linear. Unlike older log/antilog
circuits, its behavior is the same with DC and AC inputs, and DC inputs are
used for high speed testing.
Note 9: The power supply rejections of the LTC1966 are measured with
DC inputs from 50mV to 350mV. The change in accuracy from V
DD
= 2.7V
to V
DD
= 5.5V with V
SS
= 0V is divided by 2.8V. The change in accuracy
from V
SS
= 0V to V
SS
= –5.5V with V
DD
= 5.5V is divided by 5.5V.
Note 10: Previous generation RMS-to-DC converters required nonlinear
input stages as well as a nonlinear core. Some parts specify a “DC reversal
error,” combining the effects of input nonlinearity and input offset voltage.
The LTC1966 behavior is simpler to characterize and the input offset
voltage is the only significant source of “DC reversal error.”
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Characteristics
OVR Output Voltage Range ● V
SS
V
DD
V
Z
OUT
Output Impedance (Note 12) ● 75 85 95 kΩ
CMRRO Output Common Mode Rejection (Note 13) ● 16 200 µV/V
V
OMAX
Maximum Differential Output Swing Accuracy = 2%, DC Input (Note 14) 1.0 1.05 V
● 0.9 V
PSRRO Power Supply Rejection V
DD
Supply (Note 9) ● 250 1000 µV/V
V
SS
Supply (Note 9) ● 50 500 µV/V
Frequency Response
f
1P
1% Additional Error (Note 15) C
AVE
= 10µF6kHz
f
10P
10% Additional Error (Note 15) C
AVE
= 10µF20kHz
f
–3dB
±3dB Frequency (Note 15) 800 kHz
Power Supplies
V
DD
Positive Supply Voltage ● 2.7 5.5 V
V
SS
Negative Supply Voltage (Note 16) ● –5.5 0 V
I
DD
Positive Supply Current IN1 = 20mV, IN2 = 0V ● 155 170 µA
IN1 = 200mV, IN2 = 0V 158 µA
I
SS
Negative Supply Current IN1 = 20mV, IN2 = 0V ● 12 20 µA
Shutdown Characteristics
I
DDS
Supply Currents V
ENABLE
= 4.5V ● 0.5 10 µA
I
SSS
Supply Currents V
ENABLE
= 4.5V ● –1 –0.1 µA
I
IH
ENABLE Pin Current High V
ENABLE
= 4.5V ● –0.3 – 0.05 µA
I
IL
ENABLE Pin Current Low V
ENABLE
= 0.5V ● –2 –1 –0.1 µA
V
TH
ENABLE Threshold Voltage V
DD
= 5V, V
SS
= –5V 2.4 V
V
DD
= 5V, V
SS
= GND 2.1 V
V
DD
= 2.7V, V
SS
= GND 1.3 V
V
HYS
ENABLE Threshold Hysteresis 0.1 V