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PDF AS998 Data sheet ( Hoja de datos )
| Número de pieza | AS998 | |
| Descripción | Current Mode Controllers | |
| Fabricantes | Astec | |
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SEMICONDUCTOR
AS998/A
PWM Controller
Preliminary Specification
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.
Pin Configuration – Top View
8L PDIP (8N)
OV 1
Comp 2
VFB 3
ISENSE 4
8 VREG
7 VCC
6 OUT
5 GND
8L SOIC (8D)
OV 1
Comp 2
VFB
ISENSE
3
4
8 VREG
7 VCC
6 OUT
5 GND
Ordering Information
AS998/A B 8D N
Circuit Type:
PWM Controller (Models AS998 & AS998A)
Temperature Range:
B = 0°C to 105°C
www.ptcc.com.tw
233
Packaging Option:
T = Tubes
N = Tape and Reel (13" Reel Dia.)
Package Type:
8D = 8 Pin, Plastic SOIC
8N = 8 Pin, Plastic DIP
1 page  
PWM Controller
AS998/AS998A
Electrical Characteristics
Electrical Characteristics are guaranteed over full junction temperature range (0 to 105°C). Ambient temperature must be derated
based on power dissipation and package thermal characteristics. Unless otherwise specified, the conditions of test are VDD = 12 V;
OV = 0V, CSNS = 0V. Cload = 1800pf, Creg = 100 nf (AVVD to GND). To start chip, Vdd must be raised above UVLhigh.
Parameter
Symbol Test Condition
Min. Typ. Max. Unit
Startup Current
Supply Current
Startup Threshold
UVL off Threshold
Bias Current at POS
Int Regulator Voltage
Oscillator
IDDO
IDD
UVLHIGH
UVLLOW
VCLAMP
VREG
UVLHIGH Threshold
No Load
AS998
AS998A
IDD = 10mA No Load
IREG = 1mA
64 100 µA
1 2 4 mA
9 10 11 V
9.5 10 10.5 V
7.6 8 8.4 V
13 14 14.7 V
5.5 6.25 7.0
V
Parameter
Symbol Test Condition
Min. Typ. Max. Unit
Mean Period
Modulation Repetition Rate
Peak-to-Peak Modulation
Max. Duty Cycle
Error Amplifier
TOSC
TREP
TDEV
DMAX
8.4V<VDD<13.3V; 15 cycle avg. - AS998
8.4V<VDD<13.3V; 15 cycle avg. - AS998A
7.3
8.1
9.3 11.7 µs
9.3 10.7 µs
15 cycles
Peak-to-Peak change in period
13.7 16.5 23 %
70 75 78 %
Parameter
Symbol Test Condition
Min. Typ. Max. Unit
FB Divider R
VDD Regulation Point
FB Threshold
Gain (DC)
Gain-Bandwidth Product
RFB
VDDREG
VREF
AVOL
GBP
COMP = FB, VDD = 12V
No load on COMP
No load on COMP
100 kΩ
11.4 12 12.6 V
2.37 2.5 2.62 V
85 dB
10 MHz
COMP Output High
COMP Output Low
COMP Source Current
COMP Sink Current
Current Sense Comparator
VCOMPH
VCOMPL
ICOMPH
ICOMPL
FB = 2V
FB = 3V
COMP = 3V, FB = 2V
COMP = 1V, FB = 3V
4.5 V
100 250 mV
25 50 100 µA
25 300 500 µA
Parameter
Symbol Test Condition
Min. Typ. Max. Unit
Scaling of COMP
to CSNS input
0.4
AC Input Impedance
Input Filter
Prop. Delay to Output
RCSAC
FCS
tpd1
Fin ≥ FCO
Time Constant
100 kΩ
320 ns
700 ns
www.ptcc.com.tw
237
5 Page | ||
| Páginas | Total 6 Páginas | |
| PDF Descargar | [ Datasheet AS998.PDF ] | |
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