LM2931ACD2T ON Semiconductor, LM2931ACD2T Datasheet - Page 7

• Manufacturer Part Number: LM2931ACD2T
• Description: LOW DROPOUT VOLTAGE REGULATORS
• Manufacturer: ON Semiconductor

protection features making them essentially blow–out proof.
These features include internal current limiting, thermal
shutdown, overvoltage and reverse polarity input protection,
and the capability to withstand temporary power–up with
mirror–image insertion. Typical application circuits for the
fixed and adjustable output device are shown in Figures 17
and 18.
regulator is located an appreciable distance ( 4 ) from the
supply input filter. This will reduce the circuit’s sensitivity to
the input line impedance at high frequencies.
thus requires an external output capacitor for stability. The
capacitance value required is dependent upon the load
current, output voltage for the adjustable regulator, and the
type of capacitor selected. The least stable condition is
encountered at maximum load current and minimum output
voltage. Figure 22 shows that for operation in the “Stable”
region, under the conditions specified, the magnitude of the
output capacitor impedance |Z O | must not exceed 0.4 . This
limit must be observed over the entire operating temperature
range of the regulator circuit.
MOTOROLA ANALOG IC DEVICE DATA
1.240
1.220
1.200
1.180
1.160
The LM2931 series regulators are designed with many
The input bypass capacitor C in is recommended if the
This regulator series is not internally compensated and
18.5
14
Figure 15. Reference Voltage versus Output Voltage
0
3.0
Figure 13. Line Regulation
6.0
V O , OUTPUT VOLTAGE (V)
t, TIME (10 s/DIV)
9.0
12
15
LM2931C Adjustable
I O = 10 mA
V in = V out + 1.0 V
T A = 25 C
18
APPLICATIONS INFORMATION
V out = 5.0 V
R L = 500
C O = 100 F
C O(ESR) = 0.3
T A = 25 C
21
LM2931 Series
24
operation can pose a serious stability problem. As the
electrolyte freezes, around – 30 C, the capacitance will
decrease and the equivalent series resistance (ESR) will
increase drastically, causing the circuit to oscillate. Quality
electrolytic capacitors with extended temperature ranges of
– 40 to +85 C and – 55 to +105 C are readily available.
Solid tantalum capacitors may be a better choice if small size
is a requirement, however, the maximum
temperature must be observed.
linearly proportional to Z O . In effect, C O dictates the high
frequency roll–off point of the circuit. Operation in the area
titled “Marginally Stable” will cause the output of the regulator
to exhibit random bursts of oscillation that decay in an
under–damped fashion. Continuous oscillation occurs when
operating in the area titled “Unstable”. It is suggested that
oven testing of the entire circuit be performed with maximum
load, minimum input voltage, and minimum ambient
temperature.
With economical electrolytic capacitors, cold temperature
Note that in the stable region, the output noise voltage is
100
2.6
2.5
2.4
2.3
2.2
2.1
2.0
0
0
LM2931C Adjustable
I O = 10 mA
V in = V out + 1.0 V
T A = 25 C
Figure 16. Output Inhibit–Thresholds
3.0
Figure 14. Load Regulation
6.0
versus Output Voltage
V O , OUTPUT VOLTAGE (V)
t, TIME (10 s/DIV)
9.0
12
15
Output “On”
V in = 14 V
V out = 5.0 V
C in = 1000 F
C O = 100 F
C O(ESR) = 0.3
T A = 25 C
18
Z O
Output “Off”
limit over
21
7
24