DATA SHEET
SKY12340-364LF: 300 kHz – 2.0 GHz Five-Bit Digital
Attenuator with Serial-to-Parallel Driver
Applications
Cellular infrastructure
Wireless receivers
DATA_OUT
VSS
VDD
RF2
8 dB
Features
Single, +5 V DC supply voltage
Integrated silicon serial-to-parallel driver
Attenuation: 0.5 dB steps to 15.5 dB
Small, QFN (32-pin, 5 x 5 mm) Pb-free package (MSL1, 260
C
per JEDEC J-STD-020)
Serial-To-Parallel
Driver
DATA_IN
4 dB
LATCH
2 dB
CLK_IN
1 dB
RESET
0.5 dB
RF1
S1591
Figure 1. SKY12340-364LF Block Diagram
Description
The SKY12340-364LF is a GaAs FET five-bit digital attenuator I/C
with a serial-to-parallel driver. The device is provided in a
5 x 5 mm, 32-pin Quad Flat No-Lead (QFN) package.
The SKY12340-364LF is particularly suited at IF frequencies for
which high attenuation accuracy, low insertion loss, and low
intermodulation products are required.
A functional block diagram is shown in Figure 1. The pin
configuration and package are shown in Figure 2. Signal pin
assignments and functional pin descriptions are provided in
Table 1.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201111B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • January 5, 2010
1
DATA SHEET • SKY12340-364LF FIVE-BIT DIGITAL ATTENUATOR
DATA_IN
26
CLK_IN
32
31
30
29
28
27
25
LATCH
GND
VDD
VSS
C1
C2
DATA_OUT
GND
GND
GND
RF1
GND
GND
GND
1
2
3
4
5
6
7
8
24
23
22
21
20
19
18
17
RESET
GND
GND
GND
RF2
GND
GND
GND
9
10
11
12
13
14
15
16
GND
GND
GND
GND
GND
GND
GND
GND
S1584
Figure 2. SKY12340-364LF Pinout – 32-Pin QFN
(Top View)
Table 1. SKY12340-364LF Signal Descriptions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Name
DATA_OUT
GND
GND
GND
RF1
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
Description
Serial data output
Ground
Ground
Ground
RF input/output
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Pin #
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
GND
GND
GND
RF2
GND
GND
GND
RESET
LATCH
DATA_IN
CLK_IN
VSS
GND
C2
C1
VDD
Name
Ground
Ground
Ground
RF input/output
Ground
Ground
Ground
Reset
Latch enable
Serial data input
Serial clock input
Low output voltage level
Ground
Charge pump capacitor 2
Charge pump capacitor 1
Supply voltage
Description
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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January 5, 2010 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201111B
DATA SHEET • SKY12340-364LF FIVE-BIT DIGITAL ATTENUATOR
Functional Description
The SKY12340-364LF is a five bit digital attenuator comprised of
a GaAs attenuator and a silicon CMOS driver. The attenuation
setting is controlled by a serial-to-parallel interface. Attenuation is
set by a stream of data that is clocked into the shift registers of
the silicon chip by the clock signal.
To set the attenuation state, a latch signal is sent to the
appropriate pin to send the correct bias voltages to the GaAs
attenuator. The silicon chip generates a negative voltage using a
negative voltage generator that requires two external
components: a charge pump capacitor connected between pins
30 (C2) and 31 (C1) and a voltage hold capacitor connected from
pin 28 (VSS) to ground.
More than one attenuator can be cascaded together and the data
may be passed through one device to the other using the
DATA_OUT signal (pin 1). To reset the attenuator to the insertion
loss state, a logic low signal may be sent to the reset pin. DC bias
voltage to the silicon CMOS chip is applied to pin 32 (VDD).
Power-Up/Power-Down Timing
Serial data (SDA) is shifted into the register on the rising edge of
the clock (SCK), least significant bit (LSB) first. The attenuator
changes states on the rising edge of the latch-enable (LE) signal,
according to the most recent five bits of shifted data accepted
since the previous falling edge of the LE signal. Refer to the
timing diagram in Figure 3 and timing parameter specifications in
Table 2.
Power-up sequence is as follows:
0. Connect ground
1. Apply VDD
2. Set all inputs (SCK, SDA, LE)
The power-down sequence is the reverse of above.
Electrical and Mechanical Specifications
The absolute maximum ratings of the SKY12340-364LF are
provided in Table 3. Electrical specifications are provided in
Tables 4 and 5.
Typical performance characteristics of the SKY12340-364LF are
illustrated in Figures 4 through 10.
The state of the SKY12340-364LF is determined by the logic
provided in Table 6.
Data Feedthrough
LE
T1
SCK
T4
SDA
T2
T3
T5
S1594
Figure 3. Power-Up/Power-Down Timing
Table 2. Power-Up/Power-Down Timing Parameters
Parameter
LE setup time
SDA setup time
SDA hold time
LE hold time
Clock frequency
Clock period
T1
T2
T3
T4
f
CLK
T5
Symbol
Minimum
7.5
7.5
5
5
Typical
15
15
10
10
16
1/f
CLK
100
Maximum
Units
ns
ns
ns
ns
MHz
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201111B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • January 5, 2010
3
DATA SHEET • SKY12340-364LF FIVE-BIT DIGITAL ATTENUATOR
Table 3. SKY12340-364LF Absolute Maximum Ratings
Parameter
Supply voltage
Input voltage
RF input power
Storage temperature
Operating temperature
Note:
Symbol
V
DD
V
I
P
IN
T
STG
T
OP
Minimum
–0.5
–0.5 – V
DD
Typical
Maximum
+6.0
+0.5
+25
Units
V
V
dBm
C
C
–65
–40
+150
+85
Exposure to maximum rating conditions for extended periods may reduce device reliability. There is no damage to device with only one parameter set at the limit and all other
parameters set at or below their nominal value. Exceeding any of the limits listed here may result in permanent damage to the device.
CAUTION:
Although this device is designed to be as robust as possible, Electrostatic Discharge (ESD) can damage this device. This device
must be protected at all times from ESD. Static charges may easily produce potentials of several kilovolts on the human body
or equipment, which can discharge without detection. Industry-standard ESD precautions should be used at all times.
Table 4. SKY12340-364LF Electrical Specifications (Note 1)
(T
OP
= +25
C,
Characteristic Impedance [Z
O
] = 50
Ω,
V
DD
= 5 V, Unless Otherwise Noted)
Parameter
Insertion loss (Note 2)
IL
Symbol
Test Condition
300 kHz to 1.0 GHz
300 kHz to 2.0 GHz
Attenuation range (Note 3)
Attenuation accuracy (Note 3)
Return loss
Switching characteristics:
Rise, fall
On, off
Video feedthrough
1 dB input compression point
IP1dB
|S
11
|
300 kHz to 2.0 GHz
300 kHz to 2.0 GHz
10/90% or
90/10%
RF
50% control to
90/10%
RF
T
RISE
= 1 ns,
bandwidth = 500 MHz
Insertion loss state
0.5 to 2.0 GHz
0.05 GHz
3
rd
Order Intercept Point
IP3
1 MHz spacing,
P
IN
= +5 dBm/tone
Insertion loss state:
0.05 GHz
0.5 to 2.0 GHz
Attenuation states:
0.05 GHz
0.5 to 2.0 GHz
Input voltage:
High
Low
Input leakage current
Quiescent current
Supply voltage
Note 2:
Insertion loss changes by 0.003 dB/°C.
Note 3:
Attenuation value referenced above insertion loss. Exposed pad must be connected to RF ground to obtain specified attenuation.
Min
Typical
1.4
1.8
15.5
Max
1.5
2.0
Units
dB
dB
dB
±(0.35 + 2% of attenuation setting in dB)
12
20
50
100
50
dB
ns
ns
mV
+27
+26
+30
+30
dBm
dBm
+43
+47
+41
+47
1.7
0
+45
+50
+45
+50
3.5
0.3
±0.5
500
5
5.0
0.6
dBm
dBm
dBm
dBm
V
V
μA
μA
V
V
H
V
L
I
L
I
DD
V
DD
Note 1:
Performance is guaranteed only under the conditions listed in this Table.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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January 5, 2010 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • 201111B
DATA SHEET • SKY12340-364LF FIVE-BIT DIGITAL ATTENUATOR
Typical Performance Characteristics
(T
OP
= +25
C,
Characteristic Impedance [Z
O
] = 50
Ω,
V
DD
= 5 V, Unless Otherwise Noted)
0
–0.2
–0.4
–40 °C
+25 °C
+85 °C
+0.5
+0.4
+0.3
0.5 dB
1.0 dB
2.0 dB
Attenuation Error (dB)
2.00
Inseriton Loss (dB)
–0.6
–0.8
–1.0
–1.2
–1.4
–1.6
–1.8
–2.0
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
+0.2
+0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
Frequency (GHz)
Frequency (GHz)
Figure 4. Insertion Loss vs Frequency
Figure 5. Attenuation Error vs Frequency
(0.5, 1.0, and 2.0 dB States)
+0.5
+0.4
+0.3
4.0 dB
8.0 dB
15.5 dB
20
Attenuation Relative Phase (Degrees)
18
16
14
12
10
8
6
4
2
0
0
0.25
Attenuation Error (dB)
0.5 dB
1.0 dB
2.0 dB
+0.2
+0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
0.50
0.75
1.00
1.25
1.50
1.75
2.00
Frequency (GHz)
Frequency (GHz)
Figure 6. Attenuation Error vs Frequency
(4.0, 8.0, and 15.5 dB States)
Figure 7. Attenuation Relative Phase vs Frequency,
Normalized to Insertion Loss
(0.5, 1.0, and 2.0 dB States)
20
Attenuation Relative Phase (Degrees)
18
16
14
12
10
8
6
4
2
0
0
0.25
4.0 dB
8.0 dB
15.5 dB
+0.5
+0.4
+0.3
+0.2
+0.1
0
–0.1
–0.2
–0.3
–0.4
50 MHz
100 MHz
500 MHz
Attenuation Error (dB)
0.50
0.75
1.00
1.25
1.50
1.75
2.00
–0.5
0
1
2
3
4
5
6
7
8
9
10
11 12
13
14
15 16
Frequency (GHz)
Attenuation
State
(dB)
Figure 8. Attenuation Relative Phase vs Frequency,
Normalized to Insertion Loss
(4.0, 8.0, and 15.5 dB States)
Figure 9. Attenuation Error vs Attenuation State
(@ 50, 100, and 500 MHz)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201111B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • January 5, 2010
5
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