LNK454/456-458/460
DRAIN (D)
REGULATOR
5.85 V
BYPASS (BP)
UV
4.9 V
ILIM
ILIM
+
V_ILIM
CURRENT LIMIT
SOA
STATE MACHINE
SOA
SET
Q
S
R
VFB(SK)
+
Q
CLR
UV
+
VFB(LO)
+
Zero Crossing
PHASE
MEASUREMENT
VREF DAC
FILTER
IFB
V_ZLIM
1 µA
DIGITAL
INTEGRATOR
+
AUTO-RESTART
FEEDBACK (FB)
Update
CLK
INC/DEC
SET
CLR
S
R
Q
Q
FREQUENCY/
DUTY CYCLE
CONTROLLER
ON-TIME
EXTENSION
SOURCE (S)
PI-5893-091010
Figure 2. Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
D Package (SO-8C)
High-voltage power MOSFET drain connection. The internal
start-up bias current is drawn from this pin through a switched
high-voltage current source. Drain current sensing and
associated controller functions are also performed using this pin.
8
7
6
5
1
2
FB
BP
S
S
Exposed Pad (On Bottom)
Internally Connected to
SOURCE Pin
K Package
(eSOP-12)
S
S
4
SOURCE (S) Pin:
Power MOSFET source connection. Ground reference for
BYPASS and FEEDBACK pins.
D
NC 1
12 S
11 S
10 S
9 S
FB 2
BP 3
NC 4
NC 5
D 6
BYPASS (BP) Pin:
Connection point for the external bypass capacitor for the
internally generated 5.85 V supply.
8 S
7 S
Exposed Pad Internally
Connected to SOURCE Pin
FEEDBACK (FB) Pin:
V Package (eDIP-12)
LED current sensing pin. During normal operation the 290 mV
threshold determines the average value of the current flowing
through the load sense resistor.
S 12
1 NC
S 11
S 10
S 9
2 FB
3 BP
4 NC
A second threshold clamps excessive output current ripple.
A third higher threshold is used to protect against output
short-circuit and overvoltage conditions (see Figure 5).
S 8
5 NC
6 D
S 7
PI-5836a-092710
Figure 3. Pin Configuration (Top View).
2
Rev. A 11/01/10
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