L5991A STMicroelectronics, L5991A Datasheet - Page 12

• 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

L5991 - L5991A
in fig.28) holds the pin low in order to ensure that
the external MOS cannot be turned on acciden-
tally. The peculiarity of this circuit is its ability to
mantain the same sink capability (typically, 20mA
@ 1V) from V
When the threshold is exceeded and the L5991
starts operating, V
28) and the circuit is disabled.
It is then possible to omit the "bleeder" resistor
(connected between the gate and the source of
the MOS) ordinarily used to prevent undesired
switching-on of the external MOS because of
some leakage current.
Figure 28. Pull-Down of the output in UVLO.
Pin 11. PGND (Power Ground). The current loop
during the discharge of the gate of the external
MOS is closed through this pin. This loop should
be as short as possible to reduce EMI and run
separately from signal currents return.
Pin 12. SGND (Signal Ground). This ground refer-
ences the control circuitry of the IC, so all the
ground connections of the external parts related
to control functions must lead to this pin. In laying
out the PCB, care must be taken in preventing
switched high currents from flowing through the
SGND path.
Figure 29. Internal LEB.
12/23
V
REFOK
CC
ISEN
= 0V up to the start-up threshold.
REFOK
13
is pulled high (refer to fig.
I
1.2V
0
D97IN538
+
-
3V
10
12
OVERCURRENT
COMPARATOR
OUT
SGND
FROM E/A
CLK
2V
+
+
-
-
Pin 13. ISEN (Current Sense). This pin is to be
connected to the "hot" lead of the current sense
resistor R
get a voltage ramp which is an image of the cur-
rent of the switch (I
to:
the conduction of the switch is terminated.
To increase the noise immunity, a "Leading Edge
Blanking" of about 100ns is internally realized as
shown in fig. 29. Because of that, the smoothing
RC filter between this pin and R
moved or, at least, considerably reduced.
Pin 14. DIS (Device Disable). When the voltage
on pin 14 rises above 2.5V the IC is shut down
and it is necessary to pull VCC (IC supply voltage,
pin 8) below the UVLO threshold to allow the de-
vice to restart.
The pin can be driven by an external logic signal
in case of power management, as shown in fig.
30. It is also possible to realize an overvoltage
protection, as shown in the section " Application
Ideas".If used, bypass this pin to ground with a fil-
ter capacitor to avoid spurious activation due to
noise spikes. If not, it must be connected to
SGND.
Pin 15. DC-LIM (Maximum Duty Cycle Limit). The
upper extreme, Dx, of the duty cycle range de-
pends on the voltage applied to this pin. Approxi-
mately,
if DC-LIM is grounded or left floating. Instead,
COMPARATOR
V
PWM
13pk
sense
I
Qpk
D
(being the other one grounded), to
x
D97IN503
R
Q
R
sense
). When this voltage is equal
T
R
T
230
TO FAULT
TO PWM
LOGIC
LOGIC
V
COMP
10
sense
3
1.4
could be re-
9