MP7643 Exar Corporation, MP7643 Datasheet - Page 7

• Manufacturer Part Number: MP7643
• Description: 4-channel, Programmable Gain Voltage Output, 15 Mhz Input Bandwidth 8-bit Dacs With Multiplying Parallel Digital Data Port
• Manufacturer: Exar Corporation

THEORY OF OPERATION
corporates a novel open loop architecture invented by MPS.
The design produces the wider bandwidth, faster settling time,
more constant group delay, and a lower noise operation
compared to the conventional R-2R based architectures. This
device is particularly useful in applications where analog multi-
pliers are used to perform the gain adjustment function for high
frequency analog signal conditioning. Analog multipliers pro-
duce higher noise and offset. This design allows for digital con-
trol of gain with constant and very low noise from the low gain
through high gain ranges of operation.
Linearity Characteristics
(typ), and gain error  +1.5%. Since all 4 channel D/A convert-
ers are fabricated on the same IC, the linearity matching and
gain matching of +0.5% (typ) is achieved.
AC and Transient Settling Characteristics
–3 dB bandwidth. With all codes = 1 and a 1.6 V step impulse at
V
cally 150 ns (with R
and a FS to ZS or ZS to FS code change, the respective analog
output settles to 8 bits typically in 300 ns. Note that the AC per-
formance specifications also match between all 4 channels.
The above AC and transient performance is achieved with each
channel consuming only 20 mW (typ.) with either 5 V or 0 V to
10 V supplies.
Digital Interface
buses without additional I/O circuitry. Figure 1. and Figure 2.
describe the operation, specification and interface characteris-
tics of the logic port.
selected. When LD input is low the respective latch of the D/A is
enabled (digital input data becomes transparent to the latch and
the selected DAC channel), and digital data is loaded into the se-
lected DAC.
REF
The MP7643 is a 4-channel multiplying D/A converter that in-
Each DAC achieves DNL  +0.5 LSB (typ), INL  +1 LSB
The novel subranging architecture delivers a 15 MHz (typ.)
The MP7643 allows direct interface to most microprocessor
The address bits A0 and A1 determine which D/A channel is
Rev. 1.00
(1-4), the analog output settles to 8 bits of accuracy in typi-
L
= 5k to V
EE
). Also with V
REF
= 3 V or –3 V
7
Power Supplies and Voltage Reference DC Voltage
Ranges
V
V
V
V
range can, however, be set from V
8.2 V. Refer to Table 2. for the relationship equations.
–5 V. The V
V –1.8 = 3.2 V) to V
V
V
= +3.2 V. Refer to Table 2. for the relationship equations.
About the INV Input and its DC Voltage Range
INV input pin is V
of the internal circuitry around INV. If V
saturate and the amp and consequently the DAC becomes non-
functional.
of I
EE
CC
REFN
REFN
REFN
REFN
For the single supply operation, V
For the dual supply operation, V
As noted in the specification table, the max DC value of the
The min DC range of INV is limited to V
1
V
V
. Therefore, INV (min-DC) = V
= GND = 0 V. The V
–1.8 V (10 – 1.8 = 8.2 V) to V
REF
REFN
can be set at (V
DC range can be set from V
can be set to (V
is the equivalent of AGND for this DAC. In this mode
1-4
Figure 3. Simplified Block Diagram
OUT
DAC
1-4 and V
O
. Figure 3. shows a simplified block diagram
EE
CC
+1.5 V (–5 + 1.5 = –3.5 V). In this mode
CC
OUT
+ V
REF
+ V
Q2 Q1
EE
1-4 and V
1-4 range would be V
EE
V
)/2 = (10 + 0)/2 = 5 V. V
EE
)/2 = (5 – 5)/2 = 0 V. However,
V
EE
CC
EE
CC
I1
EE
EE
CC
+1.5 = 1.5 V to V
= +5, V
+1.5 V = 3.5 V to V
+1.5 V (0 + 1.5 = 1.5 V).
+1 V.
MP7643
= +10 V, V
INV
REF
be
+1
exceeds V
1-4 range would be
(Q1) and V
DD
= +5, and V
DD
CC
= +5 V, and
CC
O
–1.8 V (5
REFN
V
INV 1-4
, Q1 will
CE
CC
OUT
– 1.5 =
(sat)
–1.8
EE
DC
1-4
=