TDA9935HW NXP [NXP Semiconductors], TDA9935HW Datasheet - Page 6

• Manufacturer Part Number: TDA9935HW
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
7. Functional description
TDA9935_4
Product data sheet
Fig 3. Equivalent analog output circuit
IOUT/QOUT
The DAC is a segmented architecture composed of a 7-bit thermometer sub-DAC, and the
remaining 7-bit in a binary weighted sub-DAC.
The device produces two complementary current outputs on both channels, respectively
pins IOUT/IOUTN and QOUT/QOUTN which need to be connected via a load resistor to
the ground.
Figure 3
parallel combination of PMOS current sources and associated switches for each segment.
The cascode source configuration enables to increase the output impedance of the
source and set to improve the dynamic performance of the DAC by introducing less
distortion.
Figure 4
by the output of the internal regulator connected to the inverting input of the internal
operational amplifiers, while external resistors R
pins IVIRES and QVIRES. Thus the output current of the two DACs is typically fixed to
20 mA with an appropriate choice of these resistors. This configuration is optimal for
temperature drift compensation because the band gap can be matched with the voltage
on the feedback resistors.
The relation between full-scale output current I
The output current can also be adjusted by imposing an external reference voltage to the
inverting input pin GAPOUT and disabling the internal band gap with pin GAPD set to
HIGH. At a voltage lower than 1.2 V the current can be set at values lower than 20 mA.
The input references at pins IVIRES and QVIRES may also be driven by separate
reference voltages to adjust independently the two DAC currents.
R
I
=
AGND
R
2048 V
----------------------------------------- -
L
82
shows the equivalent analog output circuit of one DAC, which consists of a
shows the internal reference configuration. In this case the bias current is given
AGND
IOUTN/QOUTN
R
L
I
O FS
GAPOUT
TDA9935
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Rev. 04 — 17 September 2007
Dual 14-bit, up to 160 Msample/s, 2
Fig 4. Internal reference configuration
R
R
I
Q
GAPOUT
QVIRES
IVIRES
O(FS)
GAPD
AGND
I
and R
and the R
Q
TDA9935
are connected respectively to
BAND GAP
INTERNAL
I
(R
Q
) is:
TDA9935
interpolating DAC
© NXP B.V. 2007. All rights reserved.
I DAC current
sources array
Q DAC current
sources array
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