AN3001 Datasheet, PDF (7/12 Pages) M/A-COM Technology Solutions, Inc. – PIN diode Vector Modulators - Fundamentals and Drive Requirements

AN3001
Configuring the demonstration board
3.4
Optional measurement loads
As shown in Figure 2 on page 4, there are two resistors (R6 and R8) that are not connected
on the demonstration board. These resistors are used to measure the performances of the
TS4657 with different loads. After the test, it is best to remove them and load the TS4657
with the application only.
The load on both outputs should be higher or equal to 5 k. Generally, the standard load for
the audio line is 10 k (10 K/1 %, 0.063 W, SMD resistors, 0603).
3.5
Specific considerations
The TS4657 utilizes a power management unit to supply its internal structures.
A self-generated negative supply allows the drivers to be powered from positive and
negative supplies, thus increasing the output signal amplitude. This internal negative supply
switches at a higher frequency than traditional architectures, derived from the master clock
MCLK. This structure uses an original design that allows suppressing the flying or floating
capacitors. Therefore, only four small 1 µF decoupling capacitors are necessary for
VCCA/VCCD and VREGA/VREGD.
Furthermore, the self-generated negative supply allows the amplifier outputs to be centered
around zero, thus the bulky output coupling capacitors can be removed.
As mentioned previously, the MCLK is used internally to supply some blocks. It is therefore
not recommended to switch off the MCLK during normal operation.
To properly power-down the device, MCLK, BCLK and LRCLK should be switched off after
the STDBY signal.
The power-down time is very short and can be considered as zero.
Doc ID 15911 Rev 1
7/12