ISL5216_14 Datasheet, PDF (10/65 Pages) Intersil Corporation – Four-Channel Programmable Digital Downconverter

ISL5216
15-BIT MODE: 15-BIT MANTISSA (15:1), 2-BIT EXPONENT (-1, 0), 18dB MAXIMUM EXPONENT RANGE (Note 12)
EXPONENT
GAIN (dB)
PIN BIT WEIGHTING TO 16-BIT INPUT MAPPING
000
0
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 0
001
6
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 0
010
12
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 0
011
18
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 0
NOTE:
12. To select this mode, set IWA *000H/GWA F804H bits 17, 16, 8 and 7 to 1, 1, 0 and 0 respectively.
16-BIT MODE: 16-BIT MANTISSA (15:0), 1-BIT EXPONENT (-1), 6dB MAXIMUM EXPONENT RANGE (Note 13)
EXPONENT
GAIN (dB)
PIN BIT WEIGHTING TO 16-BIT INPUT MAPPING
X(-1) = 0
0
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 X0
X(-1) = 1
6
X15 X14 X13 X12 X11 X10 X9 X8 X7 X6 X5 X4 X3 X2 X1 X0
NOTE:
13. To select this mode, set IWA *000H/GWA F804H bits 17, 16, 8 and 7 to 1, 1, 0 and 1 respectively.
Level Detector
An input level detector is provided to monitor the signal level
on any of the input busses. The input bus, input format, and
the level detection type are programmable (see
Microprocessor Interface , GWA registers F804h, F805h and
F806h). This signal level represents the wideband signal from
the A/D and is useful for controlling gain/attenuation blocks
ahead of the converter.
The supported monitoring modes include integrated
magnitude (like the HSP50214 w/o the threshold) and leaky
integration (Y_n = X_n x A + Y_n-1 x (1-A)) where A = 1, 2^-8, 2^-12,
or 2^-16 (see GWA = F805h). The measurement interval can
be programmed from 2 to 65537 samples (or continuous for
the leaky integrator case). The output is 32 bits and is read via
the μP interface.
Note that the accumulators in the input level detector are 32
bits wide. This may limit the integration range to as few as
512 samples (for a 42dB exponent range).
EN
16
2^{0, -8, -12, -16}
A
B
Σ
A
NOT
S^{> UB PPORTED}
EN
MODE
R
E
G
32
FIGURE 2. PEAK DETECTOR (See “Errata” on page 63)
Y_N = A * X + (1 - A) * Y_N-1
16
X
R
Σ
E
G
Y
32
ABSOLUTE
VALUE
MSB
32
16
2^{0, -8, -12, -16}
FIGURE 1. INTEGRATED MODE
A = 2^{0, -8, -12, -16}
FIGURE 3. LEAKY INTEGRATOR
10
FN6013.3
July 13, 2007