lm5021na-2 National Semiconductor Corporation, lm5021na-2 Datasheet - Page 2

• Manufacturer Part Number: lm5021na-2
• Description: Ac-dc Current Mode Pwm Controller
• Manufacturer: National Semiconductor Corporation

www.national.com
Connection Diagram
Ordering Information
Pin Description
PIN
1
2
3
4
5
6
7
8
Order Number
LM5021MMX-1
LM5021MMX-2
LM5021MM-1
LM5021MM-2
LM5021NA-1
LM5021NA-2
RT / SYNC Oscillator timing resistor pin and
NAME
COMP
GND
VCC
OUT
VIN
CS
SS
DESCRIPTION
Control input for the Pulse Width Modulator
and Hiccup comparators.
Input voltage.
Output of a linear bias supply regulator.
Nominally 8.5V.
MOSFET gate driver output.
Ground return.
Current Sense input.
synchronization input.
Soft-start / Hiccup time
80% Duty Cycle Limit
80% Duty Cycle Limit
80% Duty Cycle Limit
50% Duty Cycle Limit
50% Duty Cycle Limit
50% Duty Cycle Limit
Description
MSOP-8 and MDIP-8
Top View
2
APPLICATION INFORMATION
COMP pull-up is provided by an internal 5K resistor
which may be used to bias an opto-coupler transistor.
Input to start-up regulator. The VIN pin is clamped at
36V by an internal zener diode.
VCC provides bias to controller and gate drive sections
of the LM5021. An external capacitor must be connected
from this pin to ground.
High current output to the external MOSFET gate input
with source/sink current capability of 0.3A and 0.7A
respectively.
Current sense input for current mode control and
over-current protection. Current limiting is accomplished
using a dedicated current sense comparator. If the CS
comparator input exceeds 0.5 Volts the OUT pin
switches low for cycle-by-cycle current limit. CS is held
low for 90ns after OUT switches high to blank the
leading edge current spike.
An external resistor connected from RT to GND sets the
oscillator frequency. This pin will also accept
synchronization pulses from an external clock.
An external capacitor and an internal 22 µA current
source set the soft-start ramp. The soft -start capacitor
controls both the soft-start rate and the hiccup mode
period.
Package Type
MSOP-8
MSOP-8
MSOP-8
MSOP-8
MDIP-8
MDIP-8
20144202
1000 Units on Tape and Reel
3500 Units on Tape and Reel
40 Units per Rail
1000 Units on Tape and Reel
3500 Units on Tape and Reel
40 Units per Rail
Supplied As