TNY253/254/255
BYPASS
REGULATOR
5.8 V
DRAIN
UNDER-VOLTAGE
+
50
µA
+
-
VI
LIMIT
OSCILLATOR
CLOCK
5.8 V
5.1 V
-
DCMAX
THERMAL
SHUTDOWN
S
Q
R
Q
1.5 V + VTH
LEADING
EDGE
BLANKING
ENABLE
SOURCE
PI-2197-061898
Figure 2. Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
Power MOSFET drain connection. Provides internal operating
current for both start-up and steady-state operation.
BYPASS (BP) Pin:
Connection point for an external bypass capacitor for the
internally generated 5.8V supply. Bypass pin is not intended
for sourcing supply current to external circuitry.
ENABLE (EN) Pin:
The power MOSFET switching can be terminated by pulling
this pin low. The I-V characteristic of this pin is equivalent to
a voltage source of approximately 1.5V with a source current
clamp of 50
µA.
SOURCE (S) Pin:
Power MOSFET source connection. Primary return.
BYPASS
1
SOURCE
2
SOURCE
3
ENABLE
4
8
7
6
5
SOURCE
SOURCE
SOURCE
DRAIN
P Package (DIP-8)
G Package (SMD-8)
PI-2199-031501
Figure 3. Pin Configuration.
circuit, Hysteretic Over Temperature Protection, Current Limit
circuit, Leading Edge Blanking, and a 700V power MOSFET.
Figure 2 shows a functional block diagram with the most
important features.
Oscillator
The oscillator frequency is internally set at 44 kHz (130 kHz for
the TNY255). The two signals of interest are the Maximum
Duty Cycle signal (D
MAX
) which runs at typically 67% duty
cycle and the Clock signal that indicates the beginning of each
cycle. When cycles are skipped (see below), the oscillator
frequency doubles (except for TNY255 which remains at
130kHz). This increases the sampling rate at the ENABLE pin
for faster loop response.
Enable (Sense and Logic)
The ENABLE pin circuit has a source follower input stage set
at 1.5V. The input current is clamped by a current source set
at 50
µA
with 10
µA
hysteresis. The output of the enable sense
TinySwitch
Functional Description
TinySwitch
is intended for low power off-line applications. It
combines a high voltage power MOSFET switch with a power
supply controller in one device. Unlike a conventional PWM
(Pulse Width Modulator) controller, the
TinySwitch
uses a
simple ON/OFF control to regulate the output voltage.
The
TinySwitch
controller consists of an Oscillator, Enable
(Sense and Logic) circuit, 5.8V Regulator, Under-Voltage
2
C
7/01
POWERINT [ POWER INTEGRATIONS, INC. ]
