L6710 STMicroelectronics, L6710 Datasheet - Page 25

• Manufacturer Part Number: L6710
• Description: IC CTRLR 6BIT 2PH PROGR 44-TQFP
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6710

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.84 ~ 1.6 V
• Current - Output: 2A
• Frequency - Switching: 150kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 44-TQFP, 44-VQFP
• Power - Output: 2.5W
• Product: Half-Bridge Drivers
• Supply Current: 12.5 mA
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Moreover, when using the low side mosfet R
connected to the PHASEx pin. DO NOT CONNECT THE PINS TOGETHER AND THEN TO THE HS
SOURCE! The device won't work properly because of the noise generated by the return of the high side
driver. In this case route two separate nets: connect the PHASEx pin to the HS Source (route together
with HGATEx) with a wide net (30 mils) and the ISENx pin to the LS Drain (route together with PGNDS).
Moreover, the PGNDS pin is always connected, through the Rg resistor, to the PGND: DO NOT CON-
NECT DIRECTLY TO THE PGND! In this case the device won't work properly. Route anyway to the LS
mosfet source (together with ISENx net).
Right and wrong connections are reported in Figure 18.
Symmetrical layout is also suggested to avoid any unbalance between the two phases of the converter.
Figure 18. PCB layout connections for sense nets.
EMBEDDING L6710-BASED VRMs…
When embedding the VRM into the application, additional care must be taken since the whole VRM is a
switching DC/DC regulator and the most common system in which it has to work is a digital system such
as MB or similar. In fact, latest MB has become faster and powerful: high speed data bus are more and
more common and switching-induced noise produced by the VRM can affect data integrity if not following
additional layout guidelines. Few easy points must be considered mainly when routing traces in which
switching high currents flow (switching high currents cause voltage spikes across the stray inductance of
the traces causing noise that can affect the near traces):
after the pin and connected through Rg to the sense point (see Fig. 17). The PCB traces connecting
these resistors to the reading point must be routed as parallel traces in order to avoid the pick-up of any
common mode noise. It's also important to avoid any offset in the measurement and to get a better pre-
cision, to connect the traces as close as possible to the sensing elements, dedicated current sense re-
sistor or low side mosfet R
– When reproducing high current path on internal layers, please keep all layers the same size in order
– Keep safe guarding distance between high current switching VRM traces and data buses, especially
– Keep safe guard distance or filter properly when routing bias traces for I/O sub-systems that must
– Possible causes of noise can be located in the PHASE connections, Mosfet gate drive and Input volt-
to avoid "surrounding" effects that increases noise coupling.
if high-speed data bus to minimize noise coupling.
walk near the VRD.
age path (from input bulk capacitors and HS drain). Also PGND connections must be considered if
not insisting on a power ground plane. These connections, that can be possible sources of noise,
must be carefully kept far away from noise-sensitive data bus.
GND Plane
VIA to
dsON
.
To LS Drain and Source
dsON
(or Sense Resistor)
as current sense element, the ISENx pin is practically
NOT CORRECT
CORRECT
To HS Gate and Source
To HS Source
(30 mils wide)
L6710
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