PRELIMINAR
Y
233
www.ptcc.com.tw
SEMICONDUCTOR
Features
• Low start-up current 64 µA (Typ)
• Low running current 2 mA (Typ)
• Low power light load mode
• Low power standby when OV is
activated
• Extended commercial operating
temperature range: 0 to 105°C
• On-board fixed frequency oscillator 100
kHz (Typ)
• Frequency randomizer to reduce EMC
emissions
• Dedicated OV shutdown pin
• On-board voltage ramp compensation
• On-board current sensing filtering
• Optional primary side regulation
Description
The AS998/AS998A is an IC intended for use as a PWM controller for
switch mode power supplies. The device is particularly suited as a pri-
mary side controller for adapter, printer, peripheral, mobile chargers and
desktop auxiliary power supplies. The AS998/AS998A is manufactured
in BICMOS technology and exhibits very low start-up and operating
power. This allows the device to be suitable in applications where strin-
gent standby or Blue Angel criteria are required.
Many of the external functions associated with PWM controllers have
been integrated into the AS998/AS998A allowing the external compo-
nent count to be significantly reduced. Features such as fixed internal
oscillator, internal ramp compensation and current filters all reduce the
external support components.
The AS998/AS998A has a typical output rise and fall time of 250/210 ns.
AS998/A
PWM Controller
Preliminary Specification
8L SOIC (8D)
1
2
3
4
8
7
6
5
V
REG
V
CC
OUT
GND
V
REG
V
CC
OUT
GND
OV
V
FB
Comp
I
SENSE
OV
V
FB
Comp
I
SENSE
8L PDIP (8N)
1
2
3
4
8
7
6
5
Pin Configuration – Top View
Circuit Type:
PWM Controller (Models AS998 & AS998A)
Temperature Range:
B = 0°C to 105°C
Packaging Option:
T = Tubes
N = Tape and Reel (13" Reel Dia.)
Package Type:
8D = 8 Pin, Plastic SOIC
8N = 8 Pin, Plastic DIP
AS998/A B 8D N
Ordering Information