L5991A STMicroelectronics, L5991A Datasheet - Page 9

• Manufacturer Part Number: L5991A
• Description: IC CTRLR PRIMARY BCD 16-DIP
• Manufacturer: STMicroelectronics

Specifications of L5991A

• Mfg Application Notes: 25W Off-Line Battery Charger with L5991A AppNote 300W Forward Converter with L5991A AppNote 45W AC-DC Adapter with Standby AppNote 60W Power Supply using the L5991 AppNote 80W Adapter using L6561/L5991A AppNote 90W SMPS for Monitors with Standby AppNote Trick Enhances L5991s Standby Function AppNote L5991-Based Converter, Temp Extra Power AppNote Auxiliary Power Supply Design AppNote Minimize Power Losses AppNote
• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 1MHz
• Duty Cycle: 93%
• Voltage - Supply: 8.2 V ~ 20 V
• Buck: No
• Boost: Yes
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: 0°C ~ 105°C
• Package / Case: 16-DIP (0.300", 7.62mm)
• Frequency-max: 1MHz
• Duty Cycle (max): 93 %
• Output Voltage: 5.075 V
• Output Current: 1500 mA
• Mounting Style: Through Hole
• Switching Frequency: 1000 KHz
• Operating Supply Voltage: 12 V to 20 V
• Maximum Operating Temperature: + 150 C
• Fall Time: 35 ns
• Minimum Operating Temperature: - 40 C
• Rise Time: 70 ns
• Synchronous Pin: Yes
• Topology: Boost, Flyback
• For Use With: 497-8226 - BOARD EVAL L5991/STP12NK80Z497-6416 - BOARD EVAL L5991/STP10NK60Z497-5083 - EVAL BOARD 3PH PWR SUPPLY W/ESBT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5722

Figure 23. Oscillator and synchronization internal schematic.
The oscillation frequency can be established with
the aid of the diagrams of fig. 14, where R
intended as the parallel of R
operation and R
the following approximate relationships:
which gives the normal operating frequency, and:
which gives the standby frequency, that is the one
the converter will operate at when lightly loaded.
In the above expressions, RA // RB means:
while K
and is related to the duration of the falling-edge of
the sawtooth:
T
ered at pin 1 and defines the upper extreme of the
duty cycle range, D
and calculation) since the output is held low dur-
ing the falling edge.
In case V15 is connected to VREF, however, the
switching frequency will be a half the values taken
d
is also the duration of the sync pulses deliv-
f
R
C
osc
A
T
T
K
f
is defined as:
SB
T
R
T
C
B
d
ST-BY
T
V
RCT
C
90 V
160
REF
30
T
R
T
0.693
A
= R
//
V
4
2
16
0.693 R
x
R
10
15
15
A
B
(see pin 15 for D
STANDBY
9
in standby, or considering
1
1
VREF
GND
R
R
R
A
A
K
A
// R
50
T
A
D1
/OPEN
CLAMP
A
R
R
C
B
B
and R
K
B
T
,
T
K
R3
4 .
T
B
2
X
3 ,
in normal
,
definition
R1
R2
1 ,
T
will be
+
-
from fig. 14 or resulting from (1) and (2).
To prevent the oscillator frequency from switching
back and forth from f
must not exceed 5.5.
If during normal operation the IC is to be synchro-
nized to an external oscillator, R
should be selected for a f
frequency in any condition (typically, 10-20% ),
depending also on the tolerance of the parts.
Pin 3. DC (Duty Cycle Control). By biasing this
pin with a voltage between 1 and 3 V it is possible
to set the maximum duty cycle between 0 and the
upper extreme D
If D
voltage V3 to be applied to pin 3 is:
D
tween V3 and the oscillator ramp (see fig. 24),
thus in case the device is synchronized to an ex-
ternal frequency f
amplitude is reduced), (5) changes into:
A voltage below 1V will inhibit the driver output
stage. This could be used for a not-latched device
disable, for example in case of overvoltage pro-
tection (see application ideas).
If no limitation on the maximum duty cycle is re-
quired (i.e. D
ing. An internal pull-up (see fig. 24) holds the volt-
age above 3V. Should the pin pick up noise (e.g.
max
max
is determined by internal comparison be-
V
3
is the desired maximum duty cycle, the
5 4
MAX
V
3
x
= D
= 5 - 2
ext
(see pin 15).
exp
X
osc
(and therefore the oscillator
), the pin has to be left float-
SYNC
D97IN729A
600 A
(2-Dmax)
to f
osc
R
1
T
SB
lower than the master
D
, the ratio f
C
max
L5991 - L5991A
T
(5)
A
f
ext
, R
D
R
CLK
Q
B
(6)
osc
and C
/ f
9/23
SB
T