TNY274-280
BYPASS/
MULTI-FUNCTION
(BP/M)
DRAIN
(D)
REGULATOR
5.85 V
LINE UNDER-VOLTAGE
115 μA
25 μA
FAULT
PRESENT
BYPASS PIN
UNDER-VOLTAGE
+
-
AUTO-
RESTART
COUNTER
BYPASS
CAPACITOR
SELECT AND
CURRENT
LIMIT STATE
MACHINE
5.85 V
4.9 V
VILIMIT
RESET
6.4 V
CURRENT LIMIT
COMPARATOR
-
ENABLE
1.0 V + VT
1.0 V
+
JITTER
CLOCK
THERMAL
SHUTDOWN
DC
MAX
OSCILLATOR
S
R
Q
Q
ENABLE/
UNDER-
VOLTAGE
(EN/UV)
LEADING
EDGE
OVP
BLANKING
LATCH
SOURCE
(S)
PI-4077-062306
Figure 2. Functional Block Diagram.
Pin Functional Description
P Package (DIP-8C)
G Package (SMD-8C)
DRAIN (D) Pin:
This pin is the power MOSFET drain connection. It provides
internal operating current for both startup and steady-state
operation.
EN/UV
BP/M
S
S
1
2
8
7
BYPASS/MULTI-FUNCTION (BP/M) Pin:
This pin has multiple functions:
6
5
S
S
ꢀ. It is the connection point for an external bypass capacitor for
the internally generated 1.81 V supply.
4
D
2. It is a mode selector for the current limit value, depending on
the value of the capacitance added. Use of a 0.ꢀ μF
capacitor results in the standard current limit value. Use of a
ꢀ μF capacitor results in the current limit being reduced to
that of the next smaller device size. Use of a ꢀ0 μF capacitor
results in the current limit being increased to that of the next
larger device size for TNY271-280.
PI-4078-080905
Figure 3. Pin Configuration.
ENABLE/UNDERVOLTAGE (EN/UV) Pin:
3. It provides a shutdown function. When the current into the
bypass pin exceeds ISD, the device latches off until the
BP/M voltage drops below 4.9 V, during a power down. This
can be used to provide an output overvoltage function with a
Zener connected from the BP/M pin to a bias winding supply.
This pin has dual functions: enable input and line undervoltage
sense. During normal operation, switching of the power
MOSFET is controlled by this pin. MOSFET switching is
terminated when a current greater than a threshold current is
drawn from this pin. Switching resumes when the current being
2
Rev. I 01/09
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