MC44604_05 ONSEMI [ON Semiconductor], MC44604_05 Datasheet - Page 18

• Manufacturer Part Number: MC44604_05
• Description: High Safety Pulsed Mode Standby GreenLine TM PWM Controller
• Manufacturer: ONSEMI [ON Semiconductor]

has started to allow the reference V
V
Undervoltage Lockout Section
been incorporated to guarantee that the IC is fully functional
before allowing operation of the system.
a comparator that has an upper threshold equal to 14,5 V
(V
normal mode and 14.5 V and 12.5 V in Standby mode
(typical values) (Note 1).
reference block that generates the voltage and current
sources required by the system.
and I
between pin 16 and the ground:
level that is nearly equal to 9 V (V
mode, a signal UVLO1 is generated to reset the maximum
duty cycle and soft−start block and so, to disable the output
stage (refer to Max. Duty Cycle and Soft−Start §) as soon as
V
reset and made ready for a next startup, before the reference
block is disabled (refer to Figure 26). In standby, UVLO1 is
not active (there is no need to discharge the soft−start
capacitor as the soft−start pin is maintained short circuited).
Note 1. In standby the difference between V
(Pin 1)
CC
CC
The overvoltage section is enabled 5 ms after the regulator
By connecting external resistors to pin 6, the threshold
As depicted in Figure 39, an undervoltage lockout has
Indeed, the V
This hysteresis comparator enables or disables the
This block particularly, produces V
In addition to this, V
V
stup−th
CC
level can be changed.
becomes lower than V
ref
I
V
frequencies.
ref
that is determined by the resistor R
) and a lower one equal to 7.5 V (V
V
9.0 V
stup−th
disable1
V
7.5 V or
12.5 V
+
1
disable
R
Figure 38. V
V
C
is decreased not to have too low pulsed mode
CC
ref
ref
UVLO1
0
is connected to the non inverting input of
where V
C
STARTUP
CC
V
(to SOFT−START)
STARTUP
14.5 V
ref enable
is compared to a second threshold
disable1
CC
ref
UVLO1
Management
+ 2.5 V (typically)
1 0
. In this way, the circuit is
disable1
ref
to stabilize.
Voltage and Current
ref
Sources Generator
Reference Block:
MC44604
) so that in normal
(pin 16 voltage)
(V
ref
ref
, I
disable2
ref
disable2
connected
Pin 16
, ...)
R
http://onsemi.com
ref
) in
and
MC44604
18
enables the output to be active, is 9.4 V (maximum value of
V
[(V
MC44604 make it ideally suited for off−line converter
applications where efficient bootstrap startup techniques are
required.
Standby Management
between the standby and normal mode and to manage each
mode in an optimal way.
to drastically reduce the power consumption.
Pulsed Mode
flyback configuration as depicted in Figure 39.
divided by the ratio:
where V
level, V
the output levels (except the mP supply voltage, V
drastically reduced by a ratio in the range of 10.
losses due to the output leakage consumption, are practically
eliminated, without having to disconnect the loads.
Startup Operations
is performed at each startup.
Voltage
disable1
Thus, finally in normal mode, the upper V
The large hysteresis and the low startup current of the
The MC44604 has been designed to detect the transitions
In standby, the device monitors a pulsed mode that enables
The MC44604 standby is preferably associated to a
In effect, by this means, all the output regulation levels are
For instance, in the case of TV or monitors applications,
Consequently, as the output voltages are reduced, the
The choice of the right configuration (normal or standby)
Input
stup−th
MC44604
Figure 39. Standby Flyback Configuration
V
stby
) and so the minimum hysteresis is 4.2 V.
HV
CC
)
min
is the standby mP supply voltage.
is the normal mode high voltage regulation
= 13.6 V].
L
p
V
V
stby
HV
V
stby
1 0
Regulator
cc
1 = Standby
0 = Normal
limit that
mP
stby
Mode
) are