AD8348 Analog Devices, AD8348 Datasheet - Page 6

• Manufacturer Part Number: AD8348
• Description: 50-1000 MHz Quadrature Demodulator
• Manufacturer: Analog Devices

AD8348
25, 26
13, 16
2, 12,
1,28
7,22
8,21
3,4,
Pin
10,
18,
20
11
14
15
17
19
23
24
27
5
6
9
QOPP, QOPN
MXIP, MXIN
VPS1, VPS2,
IOFS, QOFS
IOPN,IOPP,
LOIP,LOIN
IFIN,IFIP
VCMO
QMXO
IMXO,
COM3
COM2
ENVG
COM1
VREF
ENBL
Name
VGIN
QAIN
VPS3
IAIN
LO Input. For optimum performance, these inputs should be driven differentially. Typical input drive level is
equal to –10 dBm. To obtain a broadband 50
and LOIN.
Positive Supply for LO, IF, and Biasing & Baseband sections respectively. Each of these pins should be
decoupled with 0.1 uF and 100 pF capacitors.
I- and Q-channel differential baseband outputs. Typical output swing is equal to 2Vpp differential. The DC
common-mode voltage level on these pins is set by the voltage on VCMO.
Baseband DC common-mode voltage. The voltage applied to this pin sets the DC common-mode levels for all
the baseband outputs and inputs (IMXO, QMXO, IOPP, IOPN, QOPP, QOPN, IAIN and QAIN). This pin can
either be connected to VREF or to a reference voltage from another device, such as an ADC).
I-channel baseband amplifier input. The single-ended signal on this pin is referenced to VCMO and should have
a DC bias equal to the DC voltage on the VCMO pin. If IAIN is DC-coupled to IMXO, biasing will be provided
by IMXO. If an AC-coupled filter is placed between IMXO and IAIN, this pin can be biased from VREF through
a 1 k resistor. The gain from IAIN to the differential outputs IOPN/IOPP is 20 dB.
Ground for Biasing and Baseband sections.
I- and Q-channel mixer baseband outputs. These are low impedance (40 Ohms) outputs whose bias level is set by
the voltage on the VCMO pin. These pins are typically connected to IAIN and QAIN respectively, either
directly or through a filter. These outputs can drive a maximum current of 2.5 mA
IF Section Ground
IF Input. IFIN should be AC-coupled to ground. The single-ended IF input signal should be AC-coupled into
IFIP. The nominal differential impedance of these pins is 200 Ohms. For a broadband 50
minimum loss L-pad should be used. R
I- and Q-channel offset nulling inputs. DC offsets on the I-channel mixer output (IMXO) can be nulled by
connecting a 0.1 uF capacitor from IOFS to ground. Driving IOFS with a fixed voltage (typically from a DAC)
can extended the operating frequency range to include DC by nulling out the offset at the baseband outputs.
Reference Voltage Output. This output voltage (1V) is the main bias level for the device and can be used to
externally bias the inputs and outputs of the baseband amplifiers.
Chip Enable Input. Active high. Threshold is equal to +Vs/2.
Gain Control Input. The voltage on this pin controls the gain on the RF VGA. The gain control voltage range is
from 0.2 V to 1.2 V and corresponds to a conversion gain range from +25 dB to –18 dB. This is the gain to the
output of the mixers (i.e. QMXO and IMXO). There is an additional 20 dB of gain in the final baseband
amplifiers (IAIN to IOPP/IOPN and QAIN to QOPP/QOPN). Note that the gain control function has a negative
sense (i.e. increasing voltage decreases gain).
Auxiliary mixer inputs. If ENVG is low then the IFIP, IFIN inputs are disabled and MXIP, MXIN are enabled,
allowing the VGA to be bypassed. This is a fully differential input which should be AC coupled to the signal
source.
Q-channel baseband amplifier input. The single-ended signal on this pin is referenced to VCMO and should have
a DC bias equal to the DC voltage on the VCMO pin. If QAIN is DC-coupled to QMXO, biasing will be
provided by QMXO. If an AC-coupled filter is placed between QMXO and QAIN, this pin can be biased from
VREF through a 1 k resistor. The gain from QAIN to the differential outputs QOPN/QOPP is 20 dB.
Active high VGA enable. When ENVG is high, IFIP, IFIN inputs are enabled and MXIP, MXIN inputs are
disabled. When ENVG is low, MXIP, MXIN inputs are enabled and IFIP, IFIN inputs are disabled.
LO Section Ground
PRELIMINARY TECHNICAL DATA
PIN FUNCTION DESCRIPTIONS
series
=174 Ohms, R
- 6 -
input impedance, connect a 60.4
Description
shunt
=57.6 Ohms.
shunt resistor between LOIP
input impedance, a
Rev. PrF
2/11/03
Equiv.
Cir.