Datasheet

LTC6360
20
6360f
applicaTions inForMaTion
Interfacing to High Voltage Signals
Using the amplifier in the inverting configuration, with a
fixed input common mode voltage, allows the input signal
to traverse a swing beyond the LTC6360 supply rails.
A practical application for the inverting gain configuration
is translating a high voltage signal to a range suitable for
a low voltage SAR ADC. For a clean interface, two condi-
tions must be met:
1. The gain is selected so that full-scale signals at HV
IN
are translated at the output of the LTC6360 to the ap-
propriate full-scale range for the ADC.
2. V
OUT
= V
FS
/2 when HV
IN
is centered at HV
NOM
, where
V
FS
is the ADC full-scale input voltage and HV
NOM
is
the average level of the input voltage.
Figure 12. Interfacing a ±10V Input Signal to a 5V ADC
Applying the above constraints to the design equations
gives values for R
F
/R
G
and V1:
R
F
/ R
G
=
V
OUT(MAX)
– V
OUT(MIN)
[ ]
HV
IN(MAX)
– HV
IN(MIN)
[ ]
(9)
V
1
= [V
FS
/2 + R
F
/R
G
• HV
NOM
]/(1 + R
F
/R
G
) (10)
Applying these formulas to the case where ±10V input
signal is to be translated to a 0V to 4V full-scale range
yields the values shown in Figure 12.
Figure 13. Low Noise, True Zero 1MΩ DC Precise Photodiode
Transimpedance Amplifier
5V
V
1
1.67V
10Ω
10pF
2k10k
0.1µF
5V
6360 F12
CPO
V
DD
GND
LTC6360
OUT–IN
V
CC
V
OUT
HV
IN
CPISHDN+IN
–
+
CHARGE
PUMP
0.1µF 10µF
330pF
+
–
1.67k
10V
–10V
0V
4V
0V
2V
0.1µF
1µF
6360 F13
R6
1k
U3
LTC2054
5V
C5
0.1µF
C6
0.1µF
R2
1k
J1 NXP
BF862
–
+
U1
5V
R1
1M
10k
I
PD
R5
2k
5V
R3
10M
SFH213
PHOTODIODE
CPI
C1
50fF (PARASITIC)
C4
0.1µF
1µF
CPO CPI
–
+
LTC6360
CPO CPI
10µF