AD6636CBCZ Analog Devices Inc, AD6636CBCZ Datasheet - Page 32

• Manufacturer Part Number: AD6636CBCZ
• Description: IC DIGITAL DWNCONV 4CH 256CSPBGA
• Manufacturer: Analog Devices Inc
• Series: AD6636r

Specifications of AD6636CBCZ

• Rf Type: Cellular, CDMA2000, EDGE, GPRS, GSM
• Number Of Mixers: 1
• Secondary Attributes: Down Converter
• Current - Supply: 450mA
• Voltage - Supply: 3 V ~ 3.6 V
• Package / Case: 256-CSPBGA
• Brief Features: 4/6 Independent Wideband Processing Channel, Quadrature Correction & DC Correction For Complex Input
• Supply Voltage Range: 1.7V To 1.9V
• Operating Temperature Range: -40°C To +85°C
• Ic Function: Digital Down Converter (DDC)
• Rohs Compliant: Yes
• Pin Count: 256
• Screening Level: Industrial
• Package Type: CSPBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency: -
• Gain: -
• Noise Figure: -
• Lead Free Status / Rohs Status: Compliant

AD6636
6-Tap Fixed Coefficient Filter (FIR2)
Following the first cascade of the FIR1 and HB1 filters is the
second cascade of the FIR2 and HB2 filters. The 6-tap, fixed-
coefficient FIR2 filter is useful in providing extra alias
protection for the decimating HB2 filter in certain filter
configurations. It is a simple sum-of-products FIR filter with six
filter taps and 5-bit fixed coefficients. Note that this filter does
not decimate. The normalized coefficients used in the
implementation and the 5-bit decimal equivalent value of the
coefficients are listed in Table 16.
Table 16. 6-Tap FIR2 Filter Coefficients
Coefficient
Number
C0, C5
C1, C4
C2, C3
The user can either use or bypass this filter. Writing Logic 0 to
the FIR2 enable bit in the FIR-HB control register bypasses this
fixed-coefficient filter. The filter is useful in certain filter
configurations only and bypassing it for other applications
results in power savings. The filter is especially useful in
increasing the stop-band attenuation of the HB2 filter that
follows. Therefore, it is optimal to use both FIR2 and HB2 in a
configuration.
This filter runs at a sample rate given by one of the following
equations:
If HB1 is bypassed,
If HB1 is not bypassed,
where:
f
f
The maximum input and output rate for this filter is 75 MHz.
The response of the FIR2 filter is shown in Figure 34.
HB1
FIR2
is the input rate of the HB1 filter.
is the input rate of the FIR2 filter.
f
f
FIR2
FIR2
= f
= f
HB1
HB1
/2,
−0.125
+0.1875
+0.9375
Normalized
Coefficient
Decimal Coefficient
(5-Bit)
−2
+3
+15
Rev. A | Page 32 of 80
Decimate-by-2, Half-Band Filter (HB2)
The second stage of the second cascade of the FIR-HB block is a
decimate-by-2, half-band filter. The 27-tap, symmetric, fixed-
coefficient HB2 filter has low power consumption due to its
polyphase implementation. The filter has 20 bits of input and
output data with 12-bit coefficients. The normalized
coefficients used in the implementation and the 10-bit decimal
equivalent value of the coefficients are listed in Table 17. Other
coefficients are 0s.
Table 17. HB2 Filter Fixed Coefficients
Coefficient
Number
C1, C27
C3, C25
C5, C23
C7, C21
C9, C19
C11, C17
C13, C15
C14
Similar to the HB1 filter, the user can either use or bypass this
filter. Writing Logic 0 to the HB1 enable bit in the FIR-HB
control register bypasses this fixed-coefficient HB filter. The
filter is useful in certain filter configurations only and bypassing
it for other applications results in power savings. For example,
the filter is useful in narrow-band applications in which more
filtering is required, as compared to wide-band applications, in
which a higher output rate may prohibit the use of a decimating
filter. The response of the HB2 filter is shown in Figure 35.
–100.00
–16.67
–25.00
–33.33
–41.67
–50.00
–58.33
–66.67
–75.00
–83.33
–91.67
–8.33
Figure 34. FIR2 Filter Response to the Input Rate of the Filter
0
0
FIR2 RESPONSE
0.1
FRACTION OF FIR2 INPUT SAMPLE RATE
0.2
Normalized
Coefficient
+0.00097656
−0.00537109
+0.015
−0.0380859
+0.0825195
−0.1821289
+0.6259766
+1
0.3
0.39
0.4
0.5
0.6
0.61
0.7
Decimal Coefficient
(12-Bit)
+2
−11
+32
−78
+169
−373
+1282
+2048
0.8
0.9
–30