LTC5599IUFPBF View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC5599IUFPBF' PDF : 42 Pages View PDF
LTC5599
Applications Information
Table 2. Differential Baseband (BB) Input Impedance vs
Frequency for EN = High and VCMBB = 1.4V
BB
FREQUENCY
INPUT IMPEDANCE (W)
(MHz) REAL*
IMAG* (CAP)
REFL
COEFFICIENT
MAG ANGLE
LO FREQUENCY = 92MHz (REGISTER 0x00 = 0x79), DIGITAL GAIN = –4dB
1
1.90k
–7.17k (22.2pF)
0.900 –1.6
4
1.76k
–1.82k (21.9pF)
0.893 –6.3
10
1.25k
–751 (21.2pF)
0.854 –15
20
678
–429 (18.6pF)
0.755 –27
40
342
–308 (12.9pF)
0.585 –39
LO FREQUENCY = 150MHz (REGISTER 0x00 = 0x62), DIGITAL GAIN = –4dB
1
1.90k
–9.11k (17.5pF)
0.900 –1.3
4
1.82k
–2.30k (17.3pF)
0.896 –5.0
10
1.45k
–935 (17.0pF)
0.872 –12
20
887
–507 (15.7pF)
0.804 –23
40
441
–325 (12.2pF)
0.658 –36
100
226
–252 (6.3pF)
0.457 –51
LO FREQUENCY = 500MHz (REGISTER 0x00 = 0x2D), DIGITAL GAIN = –4dB
1
1.91k
–14.7k (10.6pF)
0.900 –0.8
4
1.89k
–3.74k (10.7pF)
0.899 –3.0
10
1.72k
–1.50k (10.7pF)
0.891 –7.7
20
1.35k
–769 (10.4pF)
0.864 –15
40
786
–426 (9.4pF)
0.785 –27
100
323
–251 (6.4pF)
0.583 –47
200
212
–190 (4.2pF)
0.478 –65
LO FREQUENCY = 500MHz (REGISTER 0x00 = 0x2D), DIGITAL GAIN = 0dB
1
1.56k
–15.0k (10.6pF)
0.879 –0.8
4
1.56k
–3.84k (10.4pF)
0.880 –3.0
10
1.48k
–1.52k (10.4pF)
0.874 –7.5
20
1.21k
–784 (10.2pF)
0.849 –15
40
753
–432 (9.2pF)
0.776 –27
100
323
–251 (6.3pF)
0.582 –47
200
213
–190 (4.2pF)
0.478 –65
LO FREQUENCY = 900MHz (REGISTER 0x00 = 0x12), DIGITAL GAIN = –4dB
1
1.91k
–17.0k (9.4pF)
0.901 –0.7
2
1.90k
–4.3k (9.3pF)
0.900 –2.7
10
1.77k
–1.72k (9.3pF)
0.893 –6.7
20
1.46k
–878 (9.1pF)
0.873 –13
40
915
–475 (8.4pF)
0.811 –24
100
371
–261 (6.1pF)
0.622 –45
200
233
–193 (4.1pF)
0.506 –62
Table 2. Differential Baseband (BB) Input Impedance vs
Frequency for EN = High and VCMBB = 1.4V (continued)
BB
FREQUENCY
INPUT IMPEDANCE (W)
(MHz) REAL*
IMAG* (CAP)
REFL
COEFFICIENT
MAG ANGLE
EN = Low (Chip Disabled, REGISTER 0X00 = 0x2E)
1
2.04k
–18.2k (8.8pF)
0.906 –0.6
2
2.02k
–4.59k (8.7pF)
0.906 –2.5
10
1.91k
–1.84k (8.7pF)
0.901 –6.3
20
1.59k
–935 (8.5pF)
0.893 –12
40
1.01k
–502 (7.9pF)
0.826 –23
100
402
–269 (5.9pF)
0.644 –43
200
246
–197 (4.0pF)
0.522 –60
*Parallel Equivalent
The circuit is optimized for a common mode voltage of 1.4V
which can be internally or externally applied. In case of AC-
coupling to the baseband pins (1.4V internally generated
bias) make sure that the high pass filter corner is not
affecting the low frequency components of the baseband
signal. Even a small error for low baseband frequencies
can result in degraded EVM.
The baseband input offset voltage depends on the source
resistance. In case of AC-coupling the 1 sigma offset is
about 1.1mV, resulting in about –46.6dBm LO leakage.
For shorted baseband pins (0Ω source resistance), the
LO leakage improves to about –50.1dBm. In case of AC-
coupling the LO leakage can be reduced by connecting a
resistor in parallel with the baseband inputs, thus lower-
ing baseband input impedance and offset. Further, the
low combined baseband input leakage current of 1.3nA
in shutdown mode retains the voltage over the coupling
capacitors, which helps to settle faster when the part is
enabled again. It is recommended to drive the baseband
inputs differentially to improve the linearity. When a DAC is
used as the signal source, a reconstruction filter should be
placed between the DAC output and the LTC5599 baseband
inputs to avoid aliasing.
Internal Gain Trim DACs
Four internal gain trim DACs (one for each baseband pin)
are configured as 11-bit each. The usable DAC input value
range is integer continuous from 64 to 2047 and 0 for
shutdown. The DACs are not intended for baseband signal
5599f
20
For more information www.linear.com/LTC5599
Share Link: 
