LCS700-708
Pin Functional Description
H Package (eSIP-16C)
VCC Pin
IC power pin. In a typical application, VCC is connected to the
12 V system standby supply via a 5 W resistor. This resistor
helps provide filtering and improves noise immunity.
Note: The system standby supply return should be connected to
the B- bus and not to the GROUND pin.
Exposed Metal
(On Package Edge)
Internally
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VREF Pin
Connected
3.4 VREF pin. An internal voltage reference network used as a
voltage source for FEEDBACK pin and DT/BF pin pull-up
resistor.
GROUND (G) Pin
G is the return node for all analog small signals. All small signal
pin bypass capacitors must be returned to this pin through short
traces, with the exception of the D-S high-voltage bypass
capacitor, and the VCCH bypass capacitor. It is internally
connected to the SOURCE pins to provide a star connection.
Do not connect the GROUND pin to the SOURCE pins,
nor to the B- bus, in the PCB layout.
Exposed Pad
(Backside) Internally
Connected to GROUND
Pin (see eSIP-16C
Package Drawing)
PI-5636-051311
OV/UV Pin
Figure 3. Pin Numbering and Designation.
Overvoltage/Undervoltage pin. B+ is sensed by this pin through
a resistor divider. The OV/UV pin implements brown-in,
brown-out, and overvoltage lockout with hysteresis. Pulling this
pin down to ground will implement a remote-off function.
SOURCE (S1), (S2) Pins
SOURCE pins of internal low-side MOSFET. These should be
connected together on the PCB, and connected to the B- from
the PFC bulk capacitor or input high-voltage DC return.
FEEDBACK (FB) Pin
Current fed into this pin determines LLC switching frequency;
higher current programs higher switching frequency. The pin
V-I characteristic resembles a diode to ground during normal
switching. An RC network between the VREF pin and
FEEDBACK pin determines the minimum operating frequency,
start-up frequency, soft-start time, and delay before start-up.
HB Pin
This is the output of the half-bridge connected MOSFETs
(Source of high-side MOSFET, Drain of low-side MOSFET), to
be connected to the LLC power train (transformer primary and
series resonant capacitor).
DEAD-TIME/BURST FREQUENCY (DT/BF) Pin
A resistor divider from VREF to ground programs dead-time,
maximum switching frequency at start-up, and burst-mode
threshold frequencies.
VCCH Pin
Floating bootstrap supply pin for the LLC high-side driver. This
pin is referenced to the HB pin, which in turn is internally
connected to the SOURCE pin of the high-side MOSFET. A
bypass/storage capacitor between VCCH and HB pins, and a
boot strap diode with a series resistor from the standby supply,
are required. The storage capacitor is refreshed every time the
lower MOSFET turns on or its body diode conducts.
CURRENT-SENSE (IS) Pin
The CURRENT-SENSE pin is used for sensing transformer
primary current, to detect overload and fault conditions, through
a current sense resistor or a capacitive divider plus sense resistor
circuit. It resembles a reverse diode to ground, and does not
require a rectifier circuit for preventing negative pulses from
reaching the pin, provided the reverse current is limited to <5 mA.
DRAIN (D) Pin
DRAIN pin of the internal high-side MOSFET. This connects to
the B+ from the PFC bulk capacitor or input high-voltage DC bus.
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Rev. B 062011
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