LTC3566EUF#PBF Linear Technology, LTC3566EUF#PBF Datasheet - Page 26

• Manufacturer Part Number: LTC3566EUF#PBF
• Description: IC USB POWER MANAGER 24-QFN
• Manufacturer: Linear Technology

Specifications of LTC3566EUF#PBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

APPLICATIONS INFORMATION
Figure 8. Higher Frequency Ground Currents Follow Their Incident
Path. Slices in the Ground Plane Cause High Voltage and Increased
Emissions.
possible and that there be an unbroken ground plane
under the IC and all of its external high frequency com-
ponents. High frequency currents, such as the V
and V
their way along the ground plane in a myriad of paths
ranging from directly back to a mirror path beneath the
incident path on the top of the board. If there are slits or
cuts in the ground plane due to other traces on that layer,
the current will be forced to go around the slits. If high
frequency currents are not allowed to fl ow back through
their natural least-area path, excessive voltage will build
up and radiated emissions will occur. There should be a
group of vias under the grounded backside of the pack-
age leading directly down to an internal ground plane. To
minimize parasitic inductance, the ground plane should
be on the second layer of the PC board.
The GATE pin for the external ideal diode controller has
extremely limited drive current. Care must be taken to
minimize leakage to adjacent PC board traces. 100nA of
leakage from this pin will introduce an offset to the 15mV
ideal diode of approximately 10mV. To minimize leakage,
the trace can be guarded on the PC board by surrounding
it with V
less than one volt higher than GATE.
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3566 family.
LTC3566/LTC3566-2
26
OUT1
OUT
currents on the LTC3566 family, tend to fi nd
connected metal, which should generally be
3566 F08
BUS
, V
IN1
,
1. Are the capacitors at V
2. Are C
3. Keep sensitive components away from the SW pins.
Battery Charger Stability Considerations
The LTC3566 family’s battery charger contains both a
constant-voltage and a constant-current control loop.
The constant-voltage loop is stable without any compen-
sation when a battery is connected with low impedance
leads. Excessive lead length, however, may add enough
series inductance to require a bypass capacitor of at least
1μF from BAT to GND. Furthermore, when the battery is
disconnected, a 4.7μF capacitor in series with a 0.2Ω to
1Ω resistor from BAT to GND is required to keep ripple
voltage low.
High value, low ESR multilayer ceramic chip capacitors
reduce the constant-voltage loop phase margin, possibly
resulting in instability. Ceramic capacitors up to 22μF may
be used in parallel with a battery, but larger ceramics should
be decoupled with 0.2Ω to 1Ω of series resistance.
In constant-current mode, the PROG pin is in the feed-
back loop rather than the battery voltage. Because of the
additional pole created by any PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the battery
charger is stable with program resistor values as high
as 25k. However, additional capacitance on this node
reduces the maximum allowed program resistor. The pole
frequency at the PROG pin should be kept above 100kHz.
Therefore, if the PROG pin has a parasitic capacitance,
C
the maximum resistance value for R
PROG
as possible to the LTC3566? These capacitors provide
the AC current to the internal power MOSFETs and their
drivers. Minimizing inductance from these capacitors
to the LTC3566 is a top priority.
C
to C
R
OUT
PROG
, the following equation should be used to calculate
IN
returns current to the GND plane, and then back
OUT
.
≤
2π • 100kHz • C
and L1 closely connected? The (-) plate of
1
BUS
PROG
, V
IN1
, and V
PROG
:
OUT1
as close
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