The ML2008 and ML2009 are digitally controlled
logarithmic gain/attenuators with a range of –24 to +24dB
in 0.1dB steps.
Easy interface to microprocessors is provided by an input
latch and control signals consisting of chip select and
write.
The interface for gain setting of the ML2008 is by an 8-bit
data word, while the ML2009 is designed to interface to a
16-bit data bus with a single write operation by hardwiring the gain/attenuation pin or LSB pin. The ML2008
can be power downed by the microprocessor utilizing a
bit in the second write operation.
FEATURES
■ Low noise0dBrnc max with +24dB gain
■ Low harmonic distortion–60dB max
■ Gain range–24 to +24dB
■ Resolution0.1dB steps
■ Flat frequency response±0.05dB from 0.3-4kHz
±0.10dB from 0.1-20kHz
■ Low supply current4mA max from ±5V supplies
■ TTL/CMOS compatible digital interface
■ ML2008 is designed to interface to an 8-bit data bus;
ML2009 to 16-bit data bus
Absolute gain accuracy is 0.05dB max over supply
tolerance of ±10% and temperature range.
These CMOS logarithmic gain/attenuators are designed for * This Part Is End Of Life As Of August 1, 2000
a wide variety of applications in telecom, audio, sonar or ** This Part Is Obsolete
general purpose function generation.
= 600Ω, dBm measurements use 600Ω as reference load, digital timing
L
NOTE 3
000000000–0.05+0.05dB
000000001–0.05+0.05dB
All other gain settings–0.1+0.1dB
All values referenced to 100000000
gain when D8 (ATTEN/GAIN) = 1,
= 8dBm when D8 (ATTEN/GAIN) = 0,
V
IN
VIN = (8dBm – Ideal Gain) in dB
100-20,000Hz–0.1+0.1dB
Relative to 1kHz
= 0, +24dB gain±100mV
IN
= 0, +24dB, 1kHz450900nv/√Hz
IN
= 8dBm, 1kHz–60dB
IN
Measure 2nd, 3rd, harmonic relative
to fundamental
= 8dBm, 1kHz+60dB
IN
C msg weighted
, 1kHz sine, VIN = 0
P-P
on V
on V
CC
SS
–60–40dB
–60–40dB
3
ML2008, ML2009
ELECTRICAL CHARACTERISTICS
(Continued)
SYMBOLPARAMETERNOTESCONDITIONSMINTYPMAXUNITS
NOTE 3
Digital and DC
V
IL
V
IH
I
IN
I
IN
I
CC
Digital Input Low Voltage40.8V
Digital Input High Voltage42.0V
Input Current, Low4V
Input Current, High4VIH = V
= GND–10µA
IH
CC
10µA
VCC Supply Current4No output load, VIL = GND,4mA
VIH = VCC, VIN = 0
I
SS
VSS Supply Current4No output load, VIL = GND,–4mA
VIH = VCC, VIN = 0
I
CCP
I
SSP
VCC Supply Current, ML20084No output load, VIL = GND,0.5mA
Powerdown Mode OnlyVIH = V
CC
VSS Supply Current, ML20084No output load, VIL = GND,–0.1mA
Powerdown Mode OnlyVIH = V
CC
AC Characteristics
t
SET
Settling Time4V
OUT
= 0.185V. Change gain from –2420µs
IN
V
to +24dB. Measure from WR rising
edge to when V
settles to within
OUT
0.05dB of final value.
t
STEP
Step Response4Gain = +24dB. V
OUT
Measure from V
= –3V to +3V step.20µs
IN
= –3V to when V
IN
OUT
V
settles to within 0.05dB of final value.
t
DS
t
DH
t
AS
t
AH
t
CSS
t
CSH
t
PW
Note 1: Absolute maximum ratings are limits beyond which the life of the integrated circuit may be impaired. All voltages unless otherwise specified are measured with
Note 2: 0°C to +70°C and –40°C to +85°C operating temperature range devices are 100% tested with temperature limits guaranteed by 100% testing, sampling, or by
Note 3: Typicals are parametric norm at 25°C.
Note 4: Parameter guaranteed and 100% production tested.
Note 5: Parameter guaranteed. Parameters not 100% tested are not in outgoing quality level calculation.
Data Setup Time450ns
Data Hold Time450ns
A0 Setup Time40ns
A0 Hold Time40ns
CS* Setup Time40ns
CS* Hold Time40ns
WR* Pulse Width450ns
respect to ground.
correlation with worst-case test conditions.
4
TIMING DIAGRAM
ML2008, ML2009
D0-D8
WR
A0
CS
TYPICAL PERFORMANCE CURVES
0
–0.5
ATTEN: VIN = 0.5V
GAIN: VIN = 0.5V
–.10
–.15
–.20
–.25
–.30
–.35
AMPLITUDE (dB)
–.40
–.45
–.50
1001K10K100K
RMS
/GAIN SETTING
RMS
FREQUENCY (Hz)
GAIN = +24dB
GAIN = +18dB
GAIN = +12dB
GAIN = +0, –24dB
AS
t
CSS
DATA
VALID
t
DS
t
PW
0
–0.5
–.10
–.15
–.20
–.25
–.30
–.35
AMPLITUDE (dB)
–.40
–.45
–.50
t
DH
t
AHt
t
CSH
ATTEN: VIN = 2V
GAIN: VIN = 2V
1001K10K100K
RMS
/GAIN SETTING
RMS
GAIN = +24dB
FREQUENCY (Hz)
GAIN = 0dB
GAIN = –24dB
Figure 2. Amplitude vs Frequency
(VIN/V
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
OUTPUT NOISE VOLTAGE (µV/√Hz)
0.2
0
101001K10K
= 0.5V
OUT
GAIN = +24dB
GAIN = +12dB
GAIN = –24dB
FREQUENCY (Hz)
RMS
)
–2
–3
–4
–5
–6
–7
OUTPUT (NOISE) (dBrnc)
–8
MSG
C
–9
–10
–24
Figure 4. Output Noise Voltage vs FrequencyFigure 5. C
Figure 3. Amplitude vs Frequency
(VIN/V
VIN = 0
–18–12–606121824
Output Noise vs Gain Setting
MSG
= 2V
OUT
GAIN SETTING (dB)
RMS
)
5
ML2008, ML2009
TYPICAL PERFORMANCE CURVES
100
ATTEN: VIN = 8dBm
GAIN: V
90
1kHZ
80
70
S/N (DB)
MSG
C
60
50
40
80
70
60
50
40
S/N + D (dB)
30
20
ATTEN: VIN = 2V
GAIN: VIN = 2V
10
–24
= 8dBm/GAIN SETTING
IN
–6–12–18–24
06121824
GAIN SETTING (dB)
Figure 6. C
RMS
RMS
–18–12–606121824
S/N vs Gain Setting
MSG
/GAIN SETTING
GAIN SETTING (dB)
VIN = 1kHz
VIN = 20kHz
VIN = 50kHz
(Continued)
0.1
.08
.06
.04
(dB)
.02
0
–.02
GAIN ERROR
–.04
–.06
–.08
–1.0
–24
–18–12–606121824
Figure 7. Gain Error vs Gain Setting
80
70
60
50
S/N + D (dB)
40
30
ATTEN: V
IN
GAIN: VIN = 0.5V
20
–24–18–12–6
= 0.5V
GAIN SETTING (dB)
RMS
/GAIN SETTING
RMS
GAIN SETTING (dB)
VIN = 1kHz
VIN = 20kHz
VIN = 50kHz
06121824
Figure 8. S/N +D vs Gain Setting (VIN/V
OUT
= 2V
RMS
)
1.0 FUNCTIONAL DESCRIPTION
The ML2008, ML2009 consists of a coarse gain stage, a
fine gain stage, an output buffer, and a µP compatible
parallel digital interface.
1.1 Gain Stages
The analog input, VIN, goes directly into the op amp input
in the coarse gain stage. The coarse gain stage has a gain
range of 0 to 22.5dB in 1.5dB steps.
The fine gain stage is cascaded onto the coarse section.
The fine gain stage has a gain range of 0 to 1.5dB in 0.1dB
steps.
Both stages can be programmed for either gain or
attenuation, thus doubling the effective gain range.
6
Figure 9. S/N +D vs Gain Setting (VIN/V
OUT
= 0.5V
RMS
The logarithmic steps in each gains stage are generated by
placing the input signal across a resistor string of 16 series
resistors. Analog switches allow the voltage to be tapped
from the resistor string at 16 points. The resistors are sized
such that each output voltage is at the proper logarithmic
ratio relative to the input signal at the top of the string.
Attenuation is implemented by using the resistor string as
a simple voltage divider, and gain is implemented by
using the resistor string as a feedback resistor around an
internal op amp.
1.2 Gain Settings
Since the coarse and fine gain stages are cascaded, their
gains can be summed logarithmically. Thus, any gain from
–24dB to +24dB in 0.1dB steps can be obtained by
combining the coarse and fine gain setting to yield the
)
ML2008, ML2009
desired gain setting. The relationship between the register
0 and 1 bits and the corresponding analog gain values is
shown in Tables 1 and 2. Note that C3-C0 select the
coarse gain, F3-F0 select the fine gain, and ATTEN/GAIN
selects either gain or attenuation.
1.3 Output Buffer
The final analog stage is the output buffer. This amplifier
has internal gain of 1 and is designed to drive 600Ω,
100pF loads. Thus, it is suitable for driving a telephone
hybrid circuit directly without any external amplifier.
The digital section is powered between VCC and GND,
or 5V. The analog section is powered between VCC and
V
and uses AGND as the reference point, or ±5V.
SS
GND and AGND are totally isolated inside the device to
minimize coupling from the digital section into the analog
section. Typically this is less than 100µV. However, AGND
and GND should be tied together physically near the
device and ideally close to the common power supply
ground connection.
Typically, the power supply rejection of VCC and V
SS
to the analog output is greater than –60dB at 1KHz. If
decoupling of the power supplies is still necessary in a
system, VCC and VSS should be decoupled with respect
to AGND.
The architecture of the digital section is shown in the
preceding black diagram.
The structure of the data registers or latches is shown in
Figures 10 and 11 for the ML2008 and ML2009,
respectively. The registers control the attenuation/gain
setting bits and with the ML2008 the power down bit.
Tables 1 and 2 describe how the data word programs the
gain.
The difference between the ML2008 and ML2009 is in the
register structure. The ML2008 is an 8-bit data bus
version. This device has one 8-bit register and one 2-bit
register to store the 9 gain setting bits and 1 powerdown
bit. Two write operations are necessary to program the full
10 data bits from eight external data pins. The address pin
A0 controls which register is being written into. The
powerdown bit, PDN, causes the device to be placed in
powerdown. When PDN = 1, the device is powered
down. In this state, the power consumption is reduced by
removing power from the analog section and forcing the
analog output, V
, to a high impedance state. While the
OUT
device is in powerdown, the digital section is still
functional and the current data word remains stored in the
registers. When PDN = 0, device is in normal operation.
The ML2009 is a 9-bit data bus version. This device has
one 9-bit register to store the 9 gain setting bits. The full 9
data bits can be programmed with one write operation
from nine external data pins.
The internal registers or latches are edge triggered. The
data is transferred from the external pins to the register
output on the rising edge of WR. The address pin, A0,
controls which register the data will be written into as
shown in Figures 1 and 2. The CS control signal selects
the device by allowing the WR signal to latch in the data
only when CS is low. When CS is high, WR is inhibited
from latching in new data into the registers.
Micro Linear reserves the right to make changes to any product herein to improve reliability, function or design.
Micro Linear does not assume any liability arising out of the application or use of any product described herein,
neither does it convey any license under its patent right nor the rights of others. The circuits contained in this
data sheet are offered as possible applications only. Micro Linear makes no warranties or representations as to
whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility
or liability for use of any application herein. The customer is urged to consult with appropriate legal counsel
before deciding on a particular application.
11
2092 Concourse Drive
San Jose, CA 95131
Tel: 408/433-5200
Fax: 408/432-0295
DS2008_09-01
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