Datasheet

MAX2078
Octal-Channel Ultrasound Front-End
with CW Doppler Mixers
_______________________________________________________________________________________ 5
AC ELECTRICAL CHARACTERISTICS—VGA MODE (continued)
( Typical Application Circuit , V
REF
= 2.475V to 2.525V, V
CC1
= 3.13V to 3.47V, V
CC2
= 4.5V to 5.25V, T
A
= 0°C to +70°C, V
GND
= 0V,
V/C = 1, NP = 0, PD = 0, D43/D42/D41/D40 = 1/0/1/0 (R
IN
= 200Ω, LNA gain = 18.5dB), D45/D44 = 1/1 (f
C
= 18MHz), f
RF
= 5MHz,
capacitance to GND at each of the VGA differential outputs is 25pF, differential capacitance across VGA outputs is 15pF, R
L
= 1kΩ
differential, reference noise less than 10nV/√Hz from 1kHz to 20MHz, DOUT loaded with 10MΩ and 60pF. Typical values are at V
CC1
= 3.3V, V
CC2
= 4.75V, T
A
= +25°C, unless otherwise noted.) (Note 5)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Measured at T
A
= +25
o
C, V
VG
+ - V
VG
- = -2V ±0.4
Measured at T
A
= +25
o
C, V
VG
+ - V
VG
- = 0V ±0.4Absolute Gain Error
Measured at T
A
= +25
o
C, V
VG
+ - V
VG
- = +2V ±0.4
dB
V
VG
+ - V
VG
- = -3V (VGA minimum gain), gain ratio with
330mV
P-P
/50mV
P-P
input tones
1.4
Input Gain Compression
LNA low gain = 12.5dB, V
VG
+ - V
VG
- = -3V (VGA
minimum gain), gain ratio with 600mV
P-P
/50mV
P-P
0.8
dB
Gain step up (V
IN
= 5mV
P-P
, gain changed from 10dB to
44dB, settling time is measured within 1dB final value)
1.4
VGA Gain Response Time
G ai n step d ow n ( V
I N
= 5m V
P - P
, g ai n chang ed fr om 44d B
to 10d B, settl i ng ti m e i s m easur ed w i thi n 1d B fi nal val ue)
1.6
µs
VGA Output Offset Under Pulsed
Overload
Overdrive is ±10mA in clamping diodes, gain at 30dB,
16 pulses at 5MHz, repetition rate 20kHz; offset is
measured at output when RF duty cycle is off
180 mV
Small-Signal Output Noise 20dB of gain, V
VG
+ - V
VG
- = -0.85V, no input signal 23 nV/√Hz
Large-Signal Output Noise
20dB of gain, V
VG
+ - V
VG
- = -0.85V, f
RF
= 5MHz,
f
NOISE
= f
RF
+ 1kHz, V
OUT
= 1V
P-P
differential
35 nV/√Hz
V
IN
= 50mV
P-P
, f
RF
= 2MHz, V
OUT
= 1V
P-P
-67
Second Harmonic (HD2)
V
IN
= 50mV
P-P
, f
RF
= 5MHz, V
OUT
= 1V
P-P
-64.2
dBc
High-Gain IM3 Distortion
V
IN
= 50mV
P-P
, f
RF1
= 5MHz, f
RF2
= 5.01MHz,
V
OUT
= 1V
P-P
(Note 11)
-52 -61 dBc
Low-Gain IM3 Distortion
D43/D42/D41/D40 = 0/0/0/1 (R
IN
= 200Ω, LNA gain =
12.5dB),V
IN
= 100mV
P-P
, f
RF1
= 5MHz, f
RF2
= 5.01MHz,
V
OUT
= 1V
P-P
(Note 11)
-50 -60 dBc
Standby Mode Power-Up
Response Time
Gain set for 26dB, f
RF
= 5MHz, V
OUT
= 1V
P-P
, settled
with in 1dB from transition on NP pin
2.1 µs
Standby Mode Power-Down
Response Time
To reach DC current target ±10% 2.0 µs
Power-Up Response Time
Gain set for 28dB, f
RF
= 5MHz, V
OUT
= 1V
P-P
, settled
within 1dB from transition on PD
2.7 ms
Power-Down Response Time
Gain set for 28dB, f
RF
= 5MHz, DC power reaches
6mW/channel, from transition on PD
5ns
Adjacent Channel Crosstalk V
OUT
= 1V
P-P
differential, f
RF
= 10MHz, 28dB of gain -58 dBc
Nonadjacent Channel Crosstalk V
OUT
= 1V
P-P
differential, f
RF
= 10MHz, 28dB of gain -71 dBc
Phase Matching Between
Channels
Gain = 28dB, V
VG
+ - V
VG
- = 0.4V, V
OUT
= 1V
P-P
,
f
RF
= 10MHz
±1.2 D eg r ees