MAX4805 [MAXIM]
Octal High-Voltage-Protected, Low-Power, Low-Noise Operational Amplifiers;
| 型号： | MAX4805 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Octal High-Voltage-Protected, Low-Power, Low-Noise Operational Amplifiers |
| 文件： | 总12页 (文件大小：1957K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
The MAX4805 and the MAX4805A differ in terms of
General Description
input-current noise, input impedance, and voltage gain.
The MAX4805/MAX4805A are octal high-voltage-protect-
Depending on the equivalent transducer source imped-
ed operational amplifiers. These devices are a fully inte-
ance, either the MAX4805 or the MAX4805A can be used
grated, very compact solution for in-probe amplification
to optimize a better noise figure.
of echo signals coming from transducers in an ultrasound
The MAX4805/MAX4805A are available in the 32-pin
system. The use of in-probe buffering improves system
TQFN package. All devices are specified for the com-
signal-to-noise ratio (SNR) for transducers featuring
high-output impedance. This results in greater penetra-
mercial 0NC to +70NC temperature range.
tion depth and sensitivity. The MAX4805/MAX4805A can
be adopted in ultrasound probes without any change
Features
S High Density/8 Channels Per Package
in the system (scanner machine). Typical applica-
tions include high-impedance piezoelectric transducers
(PZT) and capacitive micromachined ultrasonic trans-
ducers (CMUT) in-probe buffering and amplification.
The MAX4805 is optimized for PZT applications, and the
MAX4805A is optimized for CMUT applications.
S I/O Protection for TX Burst Up to ±±110
S 0ery Fast Recovery Time After TX Burst
±.5µs (typ)
S O0P for Signals Greater Than ±ꢀ.ꢁ0 (typ)
S Extremely Low Power Dissipation 8mW/ch (typ)
S 65I (typ) Low-Signal Output Impedance
S 44MHz -3dB Bandwidth (typ)
The MAX4805/MAX4805A feature eight operational
amplifiers configured in a noninverting configuration.
The small-signal output impedance of these operational
amplifiers is 65I (typ) for matching the typical cable
impedance. The low-noise amplifier features 44MHz
(typ) -3dB bandwidth and very low voltage and current
noise, ensuring excellent noise figure. The output signals
of these operational amplifiers are limited with diodes in
an antiparallel configuration to GND.
S 0oltage Gain 6dB (MAX4815) (typ), 9dB
(MAX4815A) (typ)
S Low 0oltage Noise ꢀ.ꢀn0/√Hz (typ) (MAX4815)
S Low 0oltage Noise ꢀ.ꢀn0/√Hz (typ) (MAX4815A)
S Low Current Noise ꢀ.1pA/√Hz (typ) (MAX4815)
S Low Current Noise ±.ꢁpA/√Hz (typ) (MAX4815A)
S Ultra-Small (5mm x 5mm), 3ꢀ-Pin TQFN Package
The MAX4805/MAX4805A provide HV protection for
inputs and outputs of the operational amplifiers. The
operational amplifiers inputs are protected by an exter-
nal HV capacitor. An integrated automatic high-voltage
switch protects the output of the amplifier from HV
bursts. Transmitted bursts reach the transducer through
a pair of integrated, antiparallel diodes. Each channel
is able to sustain transmission burst up to P 100V. The
high-voltage (HV) protection is automatically activated
as soon as the TX voltage is greater than Q2.7V (typ); no
dedicated TX/RX signal is required.
Applications
Ultrasound Medical Imaging, CMUT Probes
Ultrasound Medical Imaging, PZT HF Probes
Ultrasound Imaging, PZT NDT Probes
Ordering Information/Selector Guide
0OLTAGE NOISE
CURRENT NOISE
0OLTAGE GAIN
PART
APPLICATIONS
PIN-PACKAGE
(n0/√Hz)
(pA/√Hz)
(dB)
MAX4815CTJ+
2.2
2.2
2.0
1.7
5.7
PZT
32 TQFN-EP*
32 TQFN-EP*
MAX4815ACTJ+
8.7
PZT, CMUT
Note: All devices are specified over the 0°C to +70°C operating temperature range.
*EP = Exposed pad.
+Denotes a lead(Pb)-free/RoHS-compliant package.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-5242; Rev 0; 4/10
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
Junction-to-Ambient Thermal Resistance
(Note 1) .................................................................29NC/W
V
V
V
V
V
, V
- V
......................................... (V
- 0.3V) to +100V
B
JA
TX_ OUT_
TX_
IN_
GSUB
........................................................-0.5V to +0.5V
Junction-to-Case Thermal Resistance
(Note 1) ...................................................................2NC/W
OUT_
.......................................................................-0.5V to +0.5V
B
JC
, V
.............................................................-0.3V to +6V
...............................................................-6V to +0.3V
Operating Temperature Range............................. 0NC to +70NC
Storage Temperature Range............................ -65NC to +150NC
Junction Temperature ................................................... +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
CC1 CC2
, V
EE1 EE2
GSUB ..................................................................-100V to +0.3V
EN............................................................................-0.3V to +6V
Continuous Power Dissipation (T = +70NC)
A
32-Pin TQFN (derate 34.5mW/NC above +70NC)....2758.6mW
Note ±: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(V
CC1
= -V
= +2V Q2.5%, T = 0NC to +70NC, unless otherwise noted. Typical values are at V
= -V
= +2V, V
= -V
= +5V,
EE1
A
CC1
EE1
CC2
EE2
T
= +25NC.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
1.95
4.9
TYP
2
MAX
UNITS
Supply Voltage 1
Supply Voltage 2
V
CC1
V
CC2
V
V
= -V
= -V
5
V
V
CC1
CC2
EE1
5
5.1
EE2
Current consumption from
V
V
V
and V
(per channel),
= +2V,
= +5V
CC1
CC1
CC2
EE1
MAX4805
2.1
3.2
= -V
= -V
EE1
EE2
Supply Current
I
mA
CC1
CC2
from V
and V
CC1
EE1
Current consumption from
V
CC1
V
CC1
V
CC2
and V
(per channel),
= +2V,
= +5V
EE1
MAX4805A
1.9
25
3.0
50
= -V
= -V
EE1
EE2
Supply Current
from V and V
V
CC1
= -V
= +2V, V
= -V
= +5V
EE1
CC2
EE2
I
FA
FA
(per channel) (in reception)
CC2
EE2
V
V
= -V
OUT_
= +2V, V
= -100V,
CC1
EE1
GSUB
= square pulses with Q60V ampli-
tude, f = 5MHz, duty cycle = 2%,
PRF = 20kHz, C = 100pF (per channel)
Substrate Supply Current
I
10
GSUB
EXT
(in transmission)
V
V
= -V
= -V
= +2V,
= +5V
CC1
EE1
CC2
EE2
MAX4805
8.4
13.2
12.2
(per channel) (in reception)
(no signal applied)
Power Dissipation in Reception
PD1
mW
V
V
= -V
= -V
= +2V,
= +5V
CC1
EE1
CC2
EE2
MAX4805A
(per channel) (in reception)
(no signal applied)
2
Maxim Integrated
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
DC ELECTRICAL CHARACTERISTICS (continued)
(V
CC1
= -V
= +2V Q2.5%, T = 0NC to +70NC, unless otherwise noted. Typical values are at V
= -V
= +2V, V
= -V
= +5V,
EE1
A
CC1
EE1
CC2
EE2
T
= +25NC.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
= +2V, V = -100V,
GSUB
MIN
TYP
MAX
UNITS
V
V
= -V
OUT_
CC1
EE1
= square pulses with Q60V ampli-
tude, f = 5MHz, duty cycle = 2%,
Power Dissipation in
Transmission
PD2
PRF = 20kHz, C
IN_) = 100pF, C
(between TX_ and
(between TX_ and
20
mW
EXT1
EXT2
GND) = 100pF (per channel) (in transmis-
sion)
Total Supply Current in
Low-Power Mode
I
EN = GND
0.1
1
FA
mV
I
OFF
MAX4805
-20
-50
48
-3
-10
65
+20
+50
101
140
TX_ and IN_
unconnected
DC Output Bias
V
OFF
MAX4805A
T
A
T
A
= +25NC
Small-Signal Output Resistance
DC Output
R
V
V
= 50mV
OUT_
OUT
= T
to T
35
MIN
MAX
R = 100I (T = +25NC) (Note 3)
L
400
mV
OUT
A
P-P
P-P
R = 100I, THD < 5% (peak to peak),
L
Maximum Output Range
V
500
mV
OUT_P-P
f = 5MHz
R = 10kI (MAX4805)
5.1
7.8
5.7
8.7
6.1
9.2
dB
L
Voltage Gain
A
V
R = 10kI (MAX4805A)
L
dB
Transmission Diode
On-Resistance
R
ON
I = 1A
1.5
I
Transmission Drop
TX
I = 1mA
400
1.5
600
2.7
750
3.8
mV
DROP
T
= +25NC
A
A
Output Impedance R 1kI,
Positive OVP Thresholds
V
OVP+
V
V
T
T
= T
to
MIN
V
= -V
= +5V
CC2
EE2
1.0
-4.1
-4.5
4.0
-1.5
-1.0
MAX
T
= +25NC
-2.9
A
Output Impedance R 1kI,
= -V = +5V
Negative OVP Threshold
V
OVP-
T
T
= T
to
A
MIN
V
CC2
EE2
MAX
IN_ input (MAX4805)
IN_ input (MAX4805A)
2.7
4
5.4
kI
kI
Input Resistance
R
IN
15.5
24
33.0
LOGIC INPUT (EN)
Low-Level Input Voltage
0.25 x
V
IL
V
V
CC1
0.75 x
High-Level Input Voltage
Logic-Input Leakage
V
V
IH
V
CC1
I
-1
+1
FA
LEAK
Maxim Integrated
3
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
AC ELECTRICAL CHARACTERISTICS
(V
CC1
= -V
= +2V Q2.5%, T = 0NC to +70NC, unless otherwise noted. Typical values are at V
= -V
= +2V, V
= -V
= +5V,
EE1
A
CC1
EE1
CC2
EE2
T
= +25NC.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
f = 5MHz, R = 1kI, V = 20mV
P-P
MIN
TYP
MAX
UNITS
Total Harmonic Distortion
THD
-50
dB
L
IN
-3dB bandwidth, R = 75I, C = 20pF,
L
L
Bandwidth
BW
44
MHz
V
IN
= 20mV
P-P
f = 5MHz (MAX4805)
f = 12.5MHz (MAX4805A)
f = 5MHz (MAX4805)
f = 12.5MHz (MAX4805A)
f = 5MHz
2.2
2.2
2.0
1.7
70
Input-Voltage Noise on IN_
E
NOISE
nV/√Hz
Input-Current Noise on IN_
Output Impedance
I
NOISE
pA/√Hz
I
Z
OUT
MAX4805
3.8
9.1
3.5
Input Impedance
Z
f = 5MHz
kI
IN
MAX4805A
Equivalent Input Capacitance
Channel Crosstalk
C
pF
IN
f = 5MHz, V
channels), R = 1kW
= 0.5V
(adjacent
OUT
P-P
CT
-40
P 20
P 25
-43
dB
IN
V
V
= Q200mV square wave,
= Q100mV, R = 1kI (MAX4805)
IN_
OUT_
L
Slew Rate
SR
V/Fs
V
V
= Q150mV square wave,
= Q100mV, R = 1kI (MAX4805A)
IN_
OUT_
L
PSRR-
f = 5MHz, 1mV
f = 5MHz, 1mV
f = 5MHz, 1mV
P-P
P-P
P-P
V
CC1
PSRR-
Power-Supply Rejection Ratio
Signal-to-Noise Ratio
-45
dB
V
EE1
PSRR-
GSUB
-43
SNR
C
EXT
= 100pF (see Figure 1)
170
dBV
V
= -V
= +5V,
CC2
EE2
Recovery Time After a
Transmitted Pulse
t
R
Q5V P RTZ Pulse P Q60V
(see Figure 2)
1.5
Fs
Enable Time
Disable Time
t
EN signal high to normal operation
EN signal low to low-power mode
5
Fs
Fs
EN
t
1.5
DIS
Note ꢀ: All specifications are 100% tested at T = +25NC, unless otherwise noted. Limits over temperature are guaranteed by
A
design.
Note 3: Guaranteed by design. Not production tested.
4
Maxim Integrated
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Test Circuits
+5V
-5V
+2V
-2V
V
CC2
V
V
CC1
V
EE1
EE2
MAX4805/MAX4805A
(SINGLE OPERATIONAL AMPLIFIER)
TX_
IN_
V
CC2
C
EXT
V
CC1
OUT_
V
EE1
V
EE2
GND
EN
+5V
GSUB
-100V
Figure 1. SNR Test Circuit
V
CC2
V
V
- V
PULSE DIODE
MAX4805
MAX4805A
V
DIODE
1kΩ
OUT_
TX_
IN_
0V
V
PULSE
OUT_
V
OUT_
t
R
Figure 2. Recovery Time Test Circuit
Maxim Integrated
5
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Typical Operating Characteristics
(V
CC1
= -V
= +2V, V
= -V
= +5V, T = +25NC, unless otherwise noted.)
EE1
CC2
EE2
A
BANDWIDTH
vs. FREQUENCY (MAX4805)
BANDWIDTH
vs. FREQUENCY (MAX4805A)
INPUT IMPEDANCE MAGNITUDE
vs. FREQUENCY
0
-5
5
25
20
15
10
5
R = 50Ω
L
0
R = 50Ω
L
30mV
P-P
-5
-10
-15
-20
-25
-30
30mV
-10
-15
-20
-25
-30
P-P
MAX4805A
400mV
P-P
400mV
P-P
MAX4805
0
1
10
FREQUENCY (MHz)
100
1
10
100
1
10
100
100
70
FREQUENCY (MHz)
FREQUENCY (MHz)
OUTPUT IMPEDANCE MAGNITUDE
vs. FREQUENCY
THD vs. FREQUENCY
NOISE FIGURE vs. FREQUENCY
120
100
80
60
40
20
0
0
-20
-40
-60
-80
7
6
5
4
3
2
1
0
R
= 1kΩ
R
= 500Ω
S
L
MAX4805
MAX4805A
1
10
100
1
10
100
1
10
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
EQUIVALENT CURRENT INPUT NOISE
vs. FREQUENCY
EQUIVALENT VOLTAGE INPUT NOISE
vs. FREQUENCY
CURRENT CONSUMPTION
vs. TEMPERATURE
10
10
20
15
10
5
I
MAX4805
EE1
MAX4805
I
CC1
1
MAX4805
MAX4805A
I
EE2
I
CC2
MAX4805A
0.1
1
0
1
10
100
1
10
100
0
10
20
30
40
50
60
FREQUENCY (MHz)
FREQUENCY (MHz)
TEMPERATURE (°C)
6
Maxim Integrated
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Typical Operating Characteristics (continued)
(V
CC1
= -V
= +2V, V
= -V
= +5V, T = +25NC, unless otherwise noted.)
EE1
CC2
EE2 A
CURRENT CONSUMPTION
vs. TEMPERATURE
PSRR+ AND PSRR- vs. FREQUENCY
20
15
10
5
0
-10
-20
-30
-40
-50
-60
MAX4805A
MAX4805
I
EE1
GSUB
I
CC1
V
CC1
V
EE1
I
EE2
I
CC2
V
CC2
V
EE2
0
0
10
20
30
40
50
60
70
1
10
FREQUENCY (MHz)
100
TEMPERATURE (°C)
TRANSIENT RESPONSE WITH
PULSE AT ±±220m
PSRR+ AND PSRR- vs. FREQUENCY
MAX4805/5A toc13
0
-10
-20
-30
-40
-50
MAX4805A
MAX4805
TX_
200mV/div
GSUB
V
CC2
V
EE2
OUT_
200mV/div
V
CC1
V
EE1
-60
40ns/div
1
10
FREQUENCY (MHz)
100
TRANSIENT RESPONSE WITH
PULSE AT ±±150m
TRANSIENT RESPONSE WITH
PULSE AT ±±60
MAX4805/5A toc14
MAX4805/5A toc15
MAX4805A
TX_
200mV/div
OUT_
50V/div
TX_
50mV/div
OUT_
200mV/div
40ns/div
100ns/div
Maxim Integrated
7
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Pin Configuration
TOP VIEW
24 23 22 21 20 19 18 17
16
15
OUT7 25
TX7 26
OUT4
TX4
14 IN4
27
28
29
30
31
32
IN7
EN
V
V
13
12
MAX4805
MAX4805A
CC2
GSUB
IN8
EE2
11 IN3
EP
10
9
TX3
TX8
+
OUT3
OUT8
1
2
3
4
5
6
7
8
TQFN
(5mm × 5mm)
CONNECT EXPOSED PAD (EP) TO GSUB.
Pin Description
PIN
NAME
FUNCTION
Channel 1—LV Buffer Input. Connect a HV capacitor between TX1 and IN1 (see the Applications
Information section).
1
IN1
2
TX1
OUT1
GND
Channel 1—HV Buffer Input. Connect TX1 to the transducer side.
Channel 1—Buffer Output. Connect OUT1 to the cable side.
Ground
3
4, 21
5
V
Negative Op Amp Voltage Supply (-2V (typ)). Bypass V
to GND with a 100nF ceramic capacitor.
EE1
EE1
6
OUT2
TX2
Channel 2—Buffer Output. Connect OUT2 to the cable side.
7
Channel 2—HV Buffer Input. Connect TX2 to the transducer side.
Channel 2—LV Buffer Input. Connect a HV capacitor between TX2 and IN2 (see the Applications
Information section).
8
IN2
9
OUT3
TX3
Channel 3—Buffer Output. Connect OUT3 to the cable side.
Channel 3—HV Buffer Input. Connect TX3 to the transducer side.
10
Channel 3—LV Buffer Input. Connect a HV capacitor between TX3 and IN3 (see the Applications
Information section).
11
IN3
12
13
V
Negative T/R Switch Voltage Supply (-5V (typ)). Bypass V
to GND with a 100nF ceramic capacitor.
to GND with a 100nF ceramic capacitor.
EE2
EE2
V
Positive T/R Switch Voltage Supply (+5V (typ)). Bypass V
CC2
CC2
Channel 4—LV Buffer Input. Connect a HV capacitor between TX4 and IN4 (see the Applications
Information section).
14
IN4
15
16
TX4
Channel 4—HV Buffer Input. Connect TX4 to the transducer side.
Channel 4—Buffer Output. Connect OUT4 to the cable side.
OUT4
8
Maxim Integrated
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Pin Description (continued)
PIN
NAME
FUNCTION
Channel 5—LV Buffer Input. Connect a HV capacitor between TX5 and IN5 (see the Applications
Information section).
17
IN5
18
19
20
22
23
TX5
Channel 5—HV Buffer Input. Connect TX5 to the transducer side.
Channel 5—Buffer Output. Connect OUT5 to the cable side.
OUT5
V
Positive Op Amp Voltage Supply (+2V (typ)). Bypass V
to GND with a 100nF ceramic capacitor.
CC1
CC1
OUT6
TX6
Channel 6—Buffer Output. Connect OUT6 to the cable side.
Channel 6—HV Buffer Input. Connect TX6 to the transducer side.
Channel 6—LV Buffer Input. Connect a HV capacitor between TX6 and IN6 (see the Applications
Information section).
24
IN6
25
26
OUT7
TX7
Channel 7—Buffer Output. Connect OUT7 to the cable side.
Channel 7—HV Buffer Input. Connect TX7 to the transducer side.
Channel 7—LV Buffer Input. Connect a HV capacitor between TX7 and IN7 (see the Applications
Information section).
27
28
29
30
IN7
EN
Enable Input. CMOS-Level Input. Drive EN low to turn off op amp and three-state I/O. Drive EN high for
normal operation.
Substrate (lowest voltage in the system) (-100V). Bypass GSUB with a high-voltage, 100nF ceramic
capacitor to GND.
GSUB
IN8
Channel 8—LV Buffer Input. Connect a HV capacitor between TX8 and IN8 (see the Applications
Information section).
31
32
—
TX8
OUT8
EP
Channel 8—HV Buffer Input. Connect TX8 to the transducer side.
Channel 8—Buffer Output. Connect OUT8 to the cable side.
Exposed Pad. Connect EP to GSUB.
Functional Diagram
V
V
V
V
EE1
CC2
EE2
CC1
MAX4805/MAX4805A
(SINGLE OPERATIONAL AMPLIFIER)
TX_
IN_
V
CC2
V
CC1
OUT_
V
EE1
V
EE2
GND
EN
GSUB
Maxim Integrated
9
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Operational Amplifier
Detailed Description
The MAX4805 features eight low-noise amplifiers (LNA)
in a noninverting configuration with a 5.7dB (typ) gain.
The MAX4805A features 8 LNAs in a noninverting config-
uration with a 9dB (typ) gain. These LNAs are enabled/
disabled by the EN input.
The MAX4805/MAX4805A are octal high-voltage-pro-
tected operational amplifiers. These devices are a fully
integrated, very compact solution for in-probe amplifi-
cation of echo signals coming from transducers in an
ultrasound system.
Enable (EN)
Drive EN high to enable and connect all the operational
amplifiers to the OUT_ outputs. Drive EN low to disable
all the operational amplifiers and disconnect from the
OUT_ outputs. When EN is low, the transmission is still
possible and the power consumption is zero. This is
useful in Continuous Wave Doppler (CWD) mode when
typically half of the transducer array is used for transmit
and half for receive (see Table 1).
The use of in-probe buffering improves system SNR
for transducers featuring high-output impedance. This
results in greater penetration depth and sensitivity. The
MAX4805/MAX4805A can be adopted in ultrasound
probes without any change in the system (scanner
machine). Typical applications include high-impedance
PZT and CMUT in-probe buffering and amplification.
The MAX4805 is optimized for PZT applications, and the
MAX4805A is optimized for CMUT applications.
Transmit/Receive (T/R) Switch
The output of the LNA is protected by an automatic T/R
switch. When voltage at OUT_ exceeds the Q2.7V (typ)
thresholds, the switch is automatically opened (high-
impedance). The switch is automatically closed (equiva-
lent impedance 65I (typ)) when OUT_ is between the
Q2.7V (typ) thresholds. A dedicated control signal is not
required to open or close the switch in typical ultrasound
systems.
The MAX4805/MAX4805A feature eight operational
amplifiers configured in a noninverting configuration.
The small-signal output impedance of these operational
amplifiers is 65I (typ) for matching the typical cable
impedance. The low-noise amplifier features 44MHz
(typ) -3dB bandwidth and very low voltage and current
noise, ensuring excellent noise figure.
The MAX4805/MAX4805A provide HV protection for
inputs and outputs of the operational amplifiers. The
operational amplifier inputs are protected by an exter-
nal HV capacitor. An integrated automatic HV switch
protects the output of the amplifier from HV bursts.
Transmitted bursts reach the transducer through a pair
of integrated antiparallel diodes. Each channel is able to
sustain transmission bursts up to Q100V. The HV protec-
tion is automatically activated as soon as the TX voltage
is greater than Q2.7V (typ); no dedicated TX/RX signal
is required.
In addition, the switch can be controlled by the EN input.
To use the device only in transmit mode (with zero power
consumption), drive EN low. This is useful in CWD mode
when typically half of the transducer array is used for
transmit and half for receive (see Table 1).
Table ±. Truth Table
T/R SWITCH
STATUS
EN
OUT_
LNA STATUS
The MAX4805 and the MAX4805A differ in terms of
input current noise, input impedance, and voltage gain.
Depending on the equivalent transducer source imped-
ance, either the MAX4805 or the MAX4805A can be used
to optimize a better noise figure.
Low
X
Shutdown
On
Open
High
< V
Open
TH-
Closed
(In Receive
Mode)
V
TH-
< V
OUT_
High
On
On
< V
TH+
High
> V
Open
TH+
X = Don’t care.
V
TH+
V
TH-
= +2.7V (typ).
= -2.7V (typ).
10
Maxim Integrated
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
V
V
V
V
EE1
CC2
EE2
CC1
MAX4805/MAX4805A
(SINGLE OPERATIONAL AMPLIFIER)
V
CC
TX_
V
CC2
V
V
CC
CC1
C
COUP
OUT_
IN_
V
V
V
EE1
EE
V
EE2
V
EE
PP
GND
EN
GSUB
PULSER
V
NN
HEAD PROBE
MAIN FRAME
Figure 3. Ultrasound Probe Application Circuit
Applications Information
Power-On/Power-Off Sequences
The MAX4805/MAX4805A do not require special power-
The use of MAX4805/MAX4805A can result in transmit
signal attenuation. During transmission, the excitation
burst reaching the transducer is typically attenuated
because of the nonidealities of the automatic T/R switch
and because of the capacitor connected between TX_
and IN_ that results in an extra load for the transmitter.
This attenuation depends on the burst frequency and
on-transmitter source impedance. It can typically be
compensated by increasing the burst amplitude from
the system.
on/off sequencing of the V
, V
, V
, and V
CC1 EE1 CC2 EE2
supply voltage.
Note: Turn on GSUB first. Turning off GSUB last is rec-
ommended.
Supply Bypassing
, and GSUB with 100nF
Bypass V
, V
, V
, V
CC1 EE1 CC2 EE2
capacitor as close as possible to the device.
Chip Information
The capacitor connected between TX_ and IN_ can be
chosen in the 47pF to 150pF range depending on the
equivalent output impedance of the transducer. A higher
capacitance value guarantees a lower attenuation of the
received echo signal at expenses of a greater attenua-
tion of the transmit signal. Figure 3 shows a typical ultra-
sound probe application.
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages. Note that a “+”, “#”, or
“-“ in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
An accurate bypass of the voltage supply is required. In
particular, it is recommended to have bypass capacitors
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
on V
, V
, V
, V
, and GSUB pins as close
CC1 EE1 CC2 EE2
32 TQFN-EP
T3255-4
ꢀ±-1±41
as possible to the device. For noisy power supplies, a
capacitor-ictor-capacitor (CLC) filter on each voltage
supply is recommended.
Maxim Integrated
11
MAX4805/MAX4805A
Octal High-Voltage-Protected, Low-Power,
Low-Noise Operational Amplifiers
Revision History
RE0ISION RE0ISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
4/10
Initial release
—
Maxim cannot me responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves he right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
12
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
©
The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
2010 Maxim Integrated
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