LTC2158-14
8
215814f
Typical perForMance characTerisTics
LTC2158-14: Frequency Response
LTC2158-14: IVDD vs Sample Rate,
15MHz Sine Wave Input, –1dBFS
SAMPLE RATE (Msps)
240
I VDD
(mA)
280
300
320
62
186
248
260
360
340
0
124
310
215814 G19
1000
100
INPUT FREQUENCY (MHz)
INPUT
AMPLITUDE
(dBFS)
–4.0
–1.5
–1.0
–0.5
–2.5
–4.5
–2.0
–3.0
–3.5
215814 G20
LTC2158-14: IOVDD vs Sample Rate,
15MHz Sine Wave Input, –1dBFS
SAMPLE RATE (Msps)
I OVDD
(mA)
40
50
60
50
150
200
250
30
80
70
0
100
300
215814 G18
LVDS CURRENT
3.5mA
LVDS CURRENT
1.75mA
pin FuncTions
VDD(Pins1,2,15,16,17,64):1.8VAnalogPowerSupply.
Bypass to ground with 0.1F ceramic capacitors. Pins 1,
2, 64 can share a bypass capacitor. Pins 15, 16, 17 can
share a bypass capacitor.
GND (Pins 3, 6, 9, 11, 14, 18, 21, 58, Exposed Pad
Pin 65): ADC Power Ground. The exposed pad must be
soldered to the PCB ground.
AINA+ (Pin 4): Positive Differential Analog Input for
Channel A.
AINA– (Pin 5): Negative Differential Analog Input for
Channel A.
SENSE (Pin 7): Reference Programming Pin. Connecting
SENSE to VDD selects the internal reference and a ±0.66V
input range. The same input voltage range can be achieved
by applying an external 1.25V reference to SENSE.
VREF (Pin 8): Reference Voltage Output. Bypass to ground
with a 2.2F ceramic capacitor. Nominally 1.25V.
VCM(Pin10):CommonModeBiasOutput;nominallyequal
to 0.435 VDD. VCM should be used to bias the common
mode of the analog inputs. Bypass to ground with a 0.1F
ceramic capacitor.
AINB– (Pin 12): Negative Differential Analog Input for
Channel B.
AINB+ (Pin 13): Positive Differential Analog Input for
Channel B.
ENC+ (Pin 19): Encode Input. Conversion starts on the
rising edge.
ENC– (Pin 20): Encode Complement Input. Conversion
starts on the falling edge.
OGND (Pins 33, 48): Output Driver Ground.
OVDD (Pins 32, 49): 1.8V Output Driver Supply. Bypass
eachpintogroundwithseparate0.1Fceramiccapacitors.
SDO (Pin 59): Serial Interface Data Output. In serial pro-
grammingmode,(PAR/SER=0V),SDOistheoptionalserial
interface data output. Data on SDO is read back from the
mode control registers and can be latched on the falling
edge of SCK. SDO is an open-drain N-channel MOSFET
output that requires an external 2k pull-up resistor from
1.8V to 3.3V. If readback from the mode control registers
is not needed, the pull-up resistor is not necessary and
SDO can be left unconnected.