Pin Functions; Block Diagram - Linear Technology Analog Devices LT8301 Datasheet

LT8301

PIN FUNCTIONS

EN/UVLO (Pin 1): Enable/Undervoltage Lockout. The
EN/UVLO pin is used to enable the LT8301. Pull the pin
below 0.2V to shut down the LT8301. This pin has an
accurate 1.228V threshold and can be used to program a
V undervoltage lockout (UVLO) threshold using a resis-
IN
tor divider from V to ground. A 2.5µA current hysteresis
IN
allows the programming of V
function is used, tie this pin directly to V
GND (Pin 2): Ground. Tie this pin directly to local ground
plane.
R (Pin 3): Input Pin for External Feedback Resistor.
FB
Connect a resistor from this pin to the transformer primary

BLOCK DIAGRAM

V
IN
C
IN
5
V
IN
1:4
M3
25µA
R1
EN/UVLO
1
2.5µA
R2
1.228V
M4
6
UVLO hysteresis. If neither
IN
.
IN
R
FB
3
R
FB
M2
–
g
m
R
REF
10kΩ
+
1.0V
–
A1
+
REFERENCE
REGULATORS
For more information
SW pin. The ratio of the R
resistor, times a trimmed 1.0V reference voltage, deter-
mines the output voltage (plus the effect of any non-unity
transformer turns ratio). Minimize trace area at this pin.
SW (Pin 4): Drain of the 65V Internal DMOS Power
Switch. Minimize trace area at this pin to reduce EMI and
voltage spikes.
V (Pin 5): Input Supply. The V
IN
to internal circuitry and serves as a reference voltage for
the feedback circuitry connected to the R
bypass this pin to ground with a capacitor.
OSCILLATOR
–
S
A3 R
+
V
IN
www.analog.com
resistor to an internal 10k
FB
pin supplies current
IN
T1
N :1
PS
•
L L
PRI SEC
•
4
SW
BOUNDARY
DETECTOR
Q DRIVER
M1
+
R
A2
SENSE
–
GND
8301 BD
pin. Locally
FB
D
OUT
+
V
OUT
C
OUT
–
V
OUT
2
Rev. A