
ADL6316 Data Sheet
Rev. 0 | Page 14 of 37
THEORY OF OPERATION
The ADL6316 is a highly integrated transmit VGA used to
interface an RF DAC to the power amplifier in a transmitter.
The ADL6316 targets high dynamic range multicarrier
transmitter designs.
The ADL6316 offers multiple gain control options with an
integrated 20.5 dB V VA , on-chip DAC control or external
voltage control, a high linearity amplifier, an RF DSA with a
14 dB attenuation range in 0.45 dB steps, followed by the
second stage high linearity amplifier.
Putting all the building blocks of the ADL6316 together, the
signal path through the device starts with differential inputs
converted to singled-ended by the integrated balun and this
single-ended signal is then quadrature coupled by the internal
quadrature hybrid.
Next, the integrated V VA , Amplifier 1, DSA, and Amplifier 2
optimize the RF signal amplitude for performance before the RF
signal passes through the output quadrature hybrid. All the
integrated building blocks of the ADL6316 are programmable via
the SPI.
RF INPUT BALUN WITH DAC INTERFACE
NETWORK
The ADL6316 converts a single-channel, 50 Ω, input differen-
tial signal to a single-ended signal via the integrated balun.
Wideband matching allows the DAC to operate over a
frequency range from 500 MHz to 1000 MHz, and a bias tee is
included to provide dc bias for the RF DAC.
QUADRATURE HYBRID
Integrated quadrature hybrids at the RF input and RF output
allow wideband performance gain and match with a low input
and output reflection coefficient to the RF DAC and PA.
RF SIGNAL CHAIN
The RF path includes a 20.5 dB VVA, the first stage of the fixed
gain amplifier, a 14 dB DSA, and the second stage of the fixed
gain amplifier (see Figure 38). The ADL6316 has two modes of
control of the VVA attenuation: internal analog control using an
integrated 12-bit DAC and external analog control. For internal
control, use Register 0x104, Bits[3:0] and Register 0x103, Bits[7:0]
to set the attenuation. The digital bits are double buffered to
avoid major carrier glitch. For this reason, Register 0x104 must
be written before Register 0x103. For external analog control of
the VVA, a control voltage is applied to the VVA_ANALOG pin
(Pin 30). Sample register writes for VVA control are shown in
Figure 38.
Table 7. Register Writes for the Control of VVA
Address Bits Settings Description
0x105 [1:0] 00 DAC to VVA
10 VVA_ANALOG (Pin 30) to VVA
0x104 [3:0] User
defined
12-bit DAC code to set VVA
attenuation; first, write to
Register 0x104, Bits[3:0], and
then to Register 0x103, Bits[7:0]
0x103 [7:0] User
defined
Next, the fixed gain amplifier is used in a quadrature balanced
configuration. The DSA provides a 14 dB range with 0.45 dB step
resolution. The digital 5-bit DSA attenuation control is found in
Bits[4:0] of Register 0x102 and Register 0x112. Finally, the
second stage fixed gain amplifier is used in a quadrature
balanced configuration.
DAC
30
VVA_ANALOG 2
0VVA CONTROL
VVA AMP
POWER-UP
DEFAULT
IN GRAY
VVA_SRC
REGISTER 0x105, BITS[1:0]
REGISTER 0x102, BITS[4:0] (TXEN = 0)
REGISTER 0x112, BITS[4:0] (TXEN = 1)
DSA
QUADRATURE
HYBRID
AMP
VVA_ATTEN, BITS[11:0] =
REGISTER 0x104, BITS[3:0]
AND
REGISTER 0x103, BITS[7:0]
BALUN QUADRATURE
HYBRID
21830-038
Figure 38. RF Signal Chain