TNY274-280
BYPASS/
MULTI-FUNCTION
(BP/M)
REGULATOR
5.85 V
LINE UNDER-VOLTAGE
DRAIN
(D)
115
μA
25
μA
AUTO-
RESTART
COUNTER
6.4 V
RESET
FAULT
PRESENT
+
BYPASS PIN
UNDER-VOLTAGE
BYPASS
-
CAPACITOR
5.85 V
SELECT AND
4.9 V
CURRENT
LIMIT STATE
MACHINE
V
I
LIMIT
CURRENT LIMIT
COMPARATOR
ENABLE
-
+
JITTER
CLOCK
1.0 V + V
T
DCMAX
OSCILLATOR
ENABLE/
UNDER-
VOLTAGE
(EN/UV)
1.0 V
S
Q
THERMAL
SHUTDOWN
R
Q
OVP
LATCH
LEADING
EDGE
BLANKING
SOURCE
(S)
PI-4077-062306
Figure 2.
Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
This pin is the power MOSFET drain connection. It provides
internal operating current for both startup and steady-state
operation.
BYPASS/MULTI-FUNCTION (BP/M) Pin:
This pin has multiple functions:
1. It is the connection point for an external bypass capacitor for
the internally generated 5.85 V supply.
2. It is a mode selector for the current limit value, depending on
the value of the capacitance added. Use of a 0.1
μF
capacitor results in the standard current limit value. Use of a
1
μF
capacitor results in the current limit being reduced to
that of the next smaller device size. Use of a 10
μF
capacitor
results in the current limit being increased to that of the next
larger device size for TNY275-280.
3. It provides a shutdown function. When the current into the
bypass pin exceeds I
SD
, 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.
P Package (DIP-8C)
G Package (SMD-8C)
EN/UV
BP/M
1
2
8
7
6
S
S
S
S
D
4
5
PI-4078-080905
Figure 3.
Pin Configuration.
ENABLE/UNDERVOLTAGE (EN/UV) Pin:
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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