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參數(shù)資料
| 型號： | L4990A |
| 廠商： | 意法半導體 |
| 英文描述： | PRIMARY CONTROLLER |
| 中文描述： | 主控制器 |
| 文件頁數(shù)： | 4/24頁 |
| 文件大?。?/td> | 322K |
| 代理商： | L4990A |
FUNCTIONAL DESCRIPTION
The I.C. contains a standard PWM current mode
control section with improved performance with
respectto the UC384X family.
Enhanced features include start-up bias current
reduced to < 270
μ
A (typ), improved E/A perform-
ance (4MHz B/W, 1.3mA Source Current, high-
slew rate) accurate 1MHz oscillator, and also re-
duced propagationdelays in the critical path from
Current Senseto Output.
ADDITIONALFEATURES
SoftStart (SS)
An external capacitor is charged by an internal
constant current source (20
μ
A) to generate a SS
signal which clamps the E/A output
The SS pin doubles as a Fault Reset Delay func-
tion as describedbelow.
Current Limit/ Reset Delay
An internal high-speed current limit comparator
ELECTRICALCHARACTERISTICS
(continued.)
Symbol
OUTPUT SECTION
V
OL
V
OH
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Output Low Voltage
Output High Voltage
I
O
= 250mA
I
O
= 20mA; V
CC
= 12V
I
O
= 200mA; V
CC
= 12V
I
O
= 5mA; V
CC
= 20V
V
CC
= 20V V
C
= 24V
C
O
= 1nF
C
O
= 2.5nF
C
O
= 1nF
C
O
= 2.5nF
V
CC
= 0V to V
CCON
; I
sink
= 10mA
1.0
V
V
V
V
μ
A
ns
ns
ns
ns
V
10
9
10.5
10
13
100
20
35
50
70
V
OUT CLAMP
Output Clamp Voltage
Collector Leakage
Fall Time
200
60
Rise Time
100
UVLO Saturation
1.0
SUPPLY SECTION
V
CCON
Startup voltage
L4990
L4990A
L4990
L4990A
L4990
L4990A
15
7.8
9
7
5.5
0.5
100
16
8.4
10
7.6
6
0.8
270
17
9
11
8.2
V
V
V
v
V
v
μ
A
V
CCOFF
Minimum Operating Voltage
V
hys
Voltage AfterTurn-on Hysteresis
I
S
Start Up Current
Before Turn-on at:
V
CC
= V
CCON
- 0.5V
C
T
= 1nF,R
T
= 4.42k
,C
O
=1nF
(After turn on), Co =0nF
C
T
= 1nF, R
T
= 4.42k
,
450
I
op
I
q
Operating Current
Quiescent Current
12
7.0
18
10
mA
mA
I
SH
V
Z
Shutdown Current
Zener Voltage
100
21
270
25
450
30
μ
A
V
I
8
= 20mA
SYNCHRONIZATION SECTION
Master Operation
I
SOURCE
= 0.8mA
Vclock = 3.5V
Slave Operation
Low Level
High Level
VSYNC = 3.5V
V
1
I
1
Clock Amplitude
Clock Source Current
4
V
7
mA
V
1
Sync Pulse
1
V
V
3.5
0.8
I
1
Sync Pulse Current
mA
OVER CURRENT PROTECTION
V
t
Fault Threshold Voltage
DISABLE SECTION
Shutdown threshold
1.1
1.2
1.3
V
2.4
2.5
2.6
V
L4990 - L4990A
4/24
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