l6706 STMicroelectronics, l6706 Datasheet - Page 43

• Manufacturer Part Number: l6706
• Description: Vr11.1 Single Phase Controller With Integrated Driver
• Manufacturer: STMicroelectronics

L6706
20
20.1
20.2
Layout guidelines
Since the device manages control functions and high-current drivers, layout is one of the
most important things to consider when designing such high current applications. A good
layout solution can generate a benefit in lowering power dissipation on the power paths,
reducing radiation and a proper connection between signal and power ground can optimize
the performance of the control loops. Two kind of critical components and connections have
to be considered when layouting a VRM based on L6706: power components and
connections and small signal components connections.
Power components and connections
These are the components and connections where switching and high continuous current
flows from the input to the load. The first priority when placing components has to be
reserved to this power section, minimizing the length of each connection and loop as much
as possible. To minimize noise and voltage spikes (EMI and losses) these interconnections
must be a part of a power plane and anyway realized by wide and thick copper traces: loop
must be anyway minimized. The critical components, i.e. the power transistors, must be
close one to the other. The use of multi-layer printed circuit board is recommended.
Figure 26
input capacitance (C
placed close to the power section in order to eliminate the stray inductance generated by the
copper traces. Low ESR and ESL capacitors are preferred, MLCC are suggested to be
connected near the HS drain. Use proper VIAs number when power traces have to move
between different planes on the PCB in order to reduce both parasitic resistance and
inductance. Moreover, reproducing the same high-current trace on more than one PCB layer
will reduce the parasitic resistance associated to that connection.
Connect output bulk capacitor as near as possible to the load, minimizing parasitic
inductance and resistance associated to the copper trace also adding extra decoupling
capacitors along the way to the load when this results in being far from the bulk capacitor
bank.
Gate traces must be sized according to the driver RMS current delivered to the power
MOSFET. The device robustness allows managing applications with the power section far
from the controller without losing performances. External gate resistors help the device to
dissipate power resulting in a general cooling of the device. When driving multiple
MOSFETs in parallel, it is suggested to use one resistor for each MOSFET.
Small signal components and connections
These are small signal components and connections to critical nodes of the application as
well as bypass capacitors for the device supply (see
(VCC and bootstrap capacitor) close to the device and refer sensible components such as
frequency set-up resistor R
connect SGND to PGND plane in a single point to avoid that drops due to the high current
delivered causes errors in the device behavior.
Remote sensing connection must be routed as parallel nets from the FBG/VSEN pins to the
load in order to avoid the pick-up of any common mode noise. Connecting these pins in
shows the details of the power connections involved and the current loops. The
IN
), or at least a portion of the total capacitance needed, has to be
OSC
Doc ID 15698 Rev 1
, over current resistor R
Figure
OCSET
26). Locate the bypass capacitor
. Star grounding is suggested:
Layout guidelines
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