l4922 STMicroelectronics, l4922 Datasheet - Page 3

• Manufacturer Part Number: l4922
• Description: Very Low Drop Regulator With Reset
• Manufacturer: STMicroelectronics

ELECTRICAL CHARACTERISTICS (V
(*) Note 1 : The device is not operating within the range : 26 V < V
EXTERNAL COMPENSATION
Since the purposeof a voltageregulatoris to supply
a fixed output voltage in spite of supply and load
variations, the open loop gain of the regulator must
be very high at low frequencies.This may cause in-
stability as a result of the various poles present in
the loop. To avoid this instability dominant pole
compensationis used to reduce phase shiftsdue to
other poles at the unity gain frequency. The lower
the frequencyof theseother poles, the greater must
be the capacitor used to create the dominant pole
for the same DC gain.
Symbol
V
V
V
V
SVR
RT peak
V
i
RthOFF
V
RthON
V
I
V
I
V
V
V
LOAD
– V
I
SC
I
t
C6
R
D
6H
Line
q
o
R
4
i
o
Operating Input Voltage
Output Voltage
Line Regulation
Supply Voltage Rejection
Load Regulation
Dropout Voltage
Quiescent Current
Short Circuit Current
Rset Output Saturation Voltage
Power On-Off Reset out Peak
Voltage
Reset Output Leakage Current
(high level)
Reset Pulse Delay Time
Power OFF V
Delay Capacitor Charging
Current (current generator)
Power ON V
Delay Comparator Threshold
Delay Comparator Hysteresis
Parameter
o
o
Threshold
Threshold
i
= 14. 4V, – 40 C
(*) Note 1
I
T
V
I
f = 120Hz; C
V
I
T
Over Full T, I
I
I
1.5V < V
3V < V
1K
V
V
C
V
Transition; T
– 40 C
V
V
Transition
Reset out = ”1” H to L Transition
Reset out = ”0” L to H Transition
o
o
o
o
o
J
i
i
J
o
R
o
4
o
D
= 0mA to 1A
= 700mA
= 10mA to 1A
= 10mA
= 1A
= 6 to 26V; I
= 12V
= 25 C
= 25 C, I
in Regul.
@ Reset out H to L
= 3V
@ Reset out L to H
= 5V
= 100nF
i
Reset Pull-up to V
< 37 V.
O
Test Conditions
dc
O
< V
T
+ 5V
< V
J
O
RT (off)
Where the output transistor is a lateral PNP type
there is a pole in the regulation loop at a frequency
too low to be compensated by a capacitor wich can
be integrated. An external compensation is there-
fore necessary so a very high value capacitor must
be connected from the output to ground.
Theparassitic equivalentseries resistanceof theca-
pacitor used adds a zero to the regulation loop. This
zero may compromise the stability of the system
since its effect tends to cancel the effect of the pole
added. In regulatorsthis ESR must be less than 3
and the minimum capacitor value is 47 F.
o
J
o
= 47 F
RT (off)
= 1A
+ 125 C
= 25 C
= 1A
pp
O
T
, I
= 10mA
J
, I
R
R
= 8mA
+ 125 C unless otherwise specified)
= 1.6mA
O
Min.
4.75
4.70
4.8
4.9
3.2
3.7
6
V
+ 0.03V
7
25
V
Typ.
o
0.45
0.65
500
1.8
rthOFF
55
15
20
–0.15
20
5
4
0.04V
Max.
0.70
0.90
0.40
0.40
V
5.2
5.1
1.0
3.8
4.4
26
25
50
12
70
50
o
–
L4922
Unit
mV
mV
mA
mA
mV
ms
dB
V
V
V
V
V
A
V
V
V
V
V
V
V
V
A
A
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