NSC LM2926T Datasheet
LM2926/LM2927
Low Dropout Regulator with Delayed Reset
LM2926/LM2927 Low Dropout Regulator with Delayed Reset
April 1998
General Description
The LM2926 is a 5V,500mA,lowdropoutregulatorwithdelayed reset. The microprocessorresetflagis set low by thermal shutdown, short circuits, overvoltage conditions, dropout, and power-up. After the fault condition is corrected, the
reset flag remains low for a delay time determined by the delay capacitor. Hysteresis is included in the reset circuit to
prevent oscillations, and a reset output is guaranteed down
to 3.2V supply input. A latching comparator is used to discharge the delay capacitor, which guarantees a full reset
pulse even when triggered by a relatively short fault condition. A patented quiescent current reduction circuit drops the
ground pin current to 8 mA at full load when the input-output
differential is 3V or more.
Familiar PNP regulator features such as reverse battery protection, transient protection, and overvoltage shutdown are
included in the LM2926 making it suitable for use in automotive and battery operated equipment.
The LM2927 is electrically identical to the LM2926 but has a
different pin-out. The LM2927 is pin-for-pin compatible with
the L4947 and TLE4260 alternatives. The LM2926 is
pin-for-pin compatible with the LM2925.
Typical Application
Features
n 5%output accuracy over entire operating range
n Dropout voltage typically 350 mV at 500 mA output
n Externally programmed reset delay
n Short circuit proof
n Reverse battery proof
n Thermally protected
n LM2926 is pin-for-pin compatible with the LM2925
+
n P
Product Enhancement tested
Applications
n Battery operated equipment
n Microprocessor-based systems
n Portable instruments
*
Required if regulator is located far (>2") from power supply filter.
must be at least 10 µF to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible to
**C
O
the regulator. This capacitor msut be rated over the same operating temperature range as the regulator. The equivalent series resistance (ESR) of this
capacitor is critical; see curve under Typical Performance Characteristics.
DS010759-1
Connection Diagrams and Ordering Information
5–Lead TO-220
DS010759-2
Front View
Order Number LM2926T
See NS Package Number TO5A
© 1998 National Semiconductor Corporation DS010759 www.national.com
5-Lead TO-220
DS010759-14
Front View
Order Number LM2927T
See NS Package Number TO5A
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Voltage
Survival
t=100 ms 80V
t=1 ms −50V
Continuous −18V to +26V
Power Dissipation (Note 3) Internally Limited
Junction Temperature (T
) 150˚C
JMAX
Storage Temperature Range −40˚C to +150˚C
Lead Temperature
(Soldering, 10 sec.) 260˚C
Operating Ratings(Note 1)
Junction Temperature Range (T
Maximum Input Voltage 26V
) −40˚C to +125˚C
J
Reset Output Sink Current 10 mA
ESD Susceptibility (Note 2) 2 kV
Electrical Characteristics
=
V
14.4V, C
IN
REGULATOR OUTPUT
Output Voltage 5 mA ≤ I
Line Regulation I
Load Regulation 5 mA ≤ I
Quiescent Current I
Quiescent Current at Low V
Dropout Voltage (Note 6) I
Short Circuit Current V
Ripple Rejection ƒ
Output Impedance I
Output Noise 10 Hz to 100 kHz, I
Long Term Stability 20 mV/1000 Hr
=
10 µF, −40˚C ≤ T
O
≤ 125˚C, unless otherwise specified.
J
Parameter Conditions Typ Limit Units
(Note 4) (Note 5) (Limit)
≤ 500 mA, 4.85 V (min)
O
=
T
25˚C 5 V
J
5.15 V (max)
5mA≤I
≤500 mA 4.75 V (min)
O
5V
5.25 V (max)
=
5 mA, 9V ≤ V
O
≤ 16V 1 mV
IN
25 mV (max)
=
I
5 mA, 7V ≤ V
O
≤ 26V 3 mV
IN
50 mV (max)
≤ 500 mA 5 mV
O
60 mV (max)
=
5mA 2 mA
O
3 mA (max)
=
I
500 mA 8 mA
O
30 mA (max)
=
I
IN
O
5 mA, V
=
5V 3 mA
IN
10 mA (max)
=
I
O
500 mA, V
=
6V 25 mA
IN
60 mA (max)
O
=
5 mA, T
=
25˚C 60 mV
J
200 mV (max)
=
I
5 mA 300 mV (max)
O
=
I
O
500 mA, T
=
25˚C 350 mV
J
600 mV (max)
=
I
500 mA 700 mV (max)
O
=
IN
=
8V, R
1Ω 800 mA (min)
L
2A
3 A (max)
=
120 Hz, V
RIPPLE
=
I
50 mA
O
=
50 mAdc and 10 mArms
O
=
1 Vrms, 60 dB (min)
RIPPLE
@
1 kHz 100 mΩ
=
50 mA 1 mVrms
O
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Electrical Characteristics (Continued)
=
V
14.4V, C
IN
REGULATOR OUTPUT
Maximum Operational Input
Voltage
Peak Transient Input Voltage V
Reverse DC Input Voltage V
Reverse Transient Input Voltage t
RESET OUTPUT
Threshold ∆V
Output Low Voltage I
Internal Pull-Up Resistance 30 kΩ
Delay Time C
Minimum Operational V
on Power Up I
Minimum Operational V
on Power Down I
DELAY CAPACITOR PIN
Threshold Difference (∆V
Charging Current (I
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Human body model; 100 pF discharged through a 1.5 kΩ resistor.
Note 3: The maximum power dissipation is a function of T
any ambient temperature is P
down. For the LM2926 and LM2927, the junction-to-ambient thermal resistance is 53˚C/W, and the junction-to-case thermal resistance is 3˚C/W.
Note 4: Typicals are at T
Note 5: Limits are 100%guaranteed by production testing.
Note 6: Dropout voltage is the input-output differential at which the circuit ceases to regulate against any further reduction in input voltage. Dropout voltage is mea-
sured when the output voltage (V
Note 7: The reset flag is set LOW when the output voltage has dropped an amount, ∆V
=
10 µF, −40˚C ≤ T
O
≤ 125˚C, unless otherwise specified.
J
Parameter Conditions Typ Limit Units
(Note 4) (Note 5) (Limit)
Continuous 26 V (min)
O
O
r
L
≥ −0.6V, R
=
1 ms, R
O
=
L
Required for Reset Condition (Note 7) −80 mV (min)
=
≤ 7V, R
=
100Ω,t
=
L
100 ms 80 V (min)
f
100Ω −18 V (min)
100Ω −50 V (min)
−250 mV
−400 mV (max)
SINK
=
1.6 mA, V
=
3.2V 0.15
IN
0.4 V (max)
=
10 nF (See Timing Curve) 19 ms
DELAY
IN
O
DELAY
Delayed Reset Output ≤ 0.8V, 2.2 V
SINK
=
1.6 mA, R
=
100Ω 3.2 V (min)
L
Delay Reset Output ≤ 0.8V, 0.7 V
SINK
=
10 µA, V
=
0V
IN
) Change in Delay Capacitor Voltage Required 3.5 V (min)
for Reset Output to Return High 3.75 V
4.1 V (max)
) 1.0 µA (min)
DELAY
2.0 µA
3.0 µA (max)
, and θJA, and TA, and is limited by thermal shutdown. The maximum allowable power dissipation at
=
D
=
25˚C and represent the most likely parametric norm.
J
)/θJA. If this dissipation is exceeded, the die temperature will rise above 150˚C and the device will go into thermal shut-
(T
JMAX–TA
) has dropped 100 mV from the nominal value measured at V
O
JMAX
=
14.4V.
IN
, from the nominal value measured at V
O
=
14.4V.
IN
Typical Performance Characteristics
Output Voltage
DS010759-15
Low Voltage Behavior
Output at Voltage Extremes
DS010759-16
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DS010759-32
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