LTC5587IDD View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC5587IDD' PDF : 20 Pages View PDF
LTC5587
APPLICATIONS INFORMATION
Conversion Range
The VREF pin defines the full-scale range of the ADC. The
reference voltage can range from VDD down to 1.4V. If
the difference between the input voltage on the VOUT pin
and GND exceeds VREF, the output code will stay fixed at
all ones, and if this difference goes below 0V, the output
code will stay fixed at all zeros. Figure 15 shows the ideal
input/output characteristics for the ADC. The code tran-
sitions occur midway between successive integer LSB
values (i.e., 0.5LSB, 1.5LSB, 2.5LSB, …, FS – 1.5LSB).
The output code is straight binary with 1LSB = VREF/4096.
Using the onboard 1.8V reference on the evaluation board,
the conversion range can be easily calculated between LSB
and dBm. For an analog output slope of 32mV/dB, we can
calculate the total 40dB range is equivalent to 2912.7LSB’s
at the ADC output:
40dB = (40dB • 4096LSB • 32mV/dB)/1.8V = 2912.7LSB
Detector Enable Pin
A simplified schematic of the EN pin is shown in Figure 16.
To enable the LTC5587 detector it is necessary to put
greater than 2V on this pin. To disable or turn off the
detector, this voltage should be below 0.3V. At an enable
voltage of 3.3V the pin draws roughly 20μA. If the EN pin
is not connected, the detector circuitry is disabled through
an internal 500k pull-down resistor.
It is important that the voltage applied to the EN pin
should never exceed VCC by more than 0.5V. Otherwise,
the supply current may be sourced through the upper ESD
protection diode connected at the EN pin.
111...111
111...110
000...001
000...000
0
1LSB
INPUT VOLTAGE (V)
FS – 1LSB
5587 F15
Figure 15. ADC Transfer Characteristics
VCC
LTC5587
9 EN
500k
300k
300k
5587 F16
Figure 16. Enable Pin Simplified Schematic
5587f
18
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