NSC LM2927T, LM2927S Datasheet
LM2926/LM2927
Low Dropout Regulator with Delayed Reset
General Description
The LM2926 is a 5V,500mA,lowdropoutregulatorwithdelayed reset. The microprocessorresetflagisset 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.
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
Typical Application
Connection Diagrams and Ordering Information
DS010759-1
*
Required if regulator is located far (>2") from power supply filter.
**C
O
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
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.
5–Lead TO-220
DS010759-2
Front View
Order Number LM2926T
See NS Package Number TO5A
5-Lead TO-220
DS010759-14
Front View
Order Number LM2927T
See NS Package Number TO5A
April 1998
LM2926/LM2927 Low Dropout Regulator with Delayed Reset
© 1998 National Semiconductor Corporation DS010759 www.national.com
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
Reset Output Sink Current 10 mA
ESD Susceptibility (Note 2) 2 kV
Power Dissipation (Note 3) Internally Limited
Junction Temperature (T
JMAX
) 150˚C
Storage Temperature Range −40˚C to +150˚C
Lead Temperature
(Soldering, 10 sec.) 260˚C
Operating Ratings(Note 1)
Junction Temperature Range (T
J
) −40˚C to +125˚C
Maximum Input Voltage 26V
Electrical Characteristics
V
IN
=
14.4V, C
O
=
10 µF, −40˚C ≤ T
J
≤ 125˚C, unless otherwise specified.
Parameter Conditions Typ Limit Units
(Note 4) (Note 5) (Limit)
REGULATOR OUTPUT
Output Voltage 5 mA ≤ I
O
≤ 500 mA, 4.85 V (min)
T
J
=
25˚C 5 V
5.15 V (max)
5mA≤I
O
≤500 mA 4.75 V (min)
5V
5.25 V (max)
Line Regulation I
O
=
5 mA, 9V ≤ V
IN
≤ 16V 1 mV
25 mV (max)
I
O
=
5 mA, 7V ≤ V
IN
≤ 26V 3 mV
50 mV (max)
Load Regulation 5 mA ≤ I
O
≤ 500 mA 5 mV
60 mV (max)
Quiescent Current I
O
=
5mA 2 mA
3 mA (max)
I
O
=
500 mA 8 mA
30 mA (max)
Quiescent Current at Low V
IN
I
O
=
5 mA, V
IN
=
5V 3 mA
10 mA (max)
I
O
=
500 mA, V
IN
=
6V 25 mA
60 mA (max)
Dropout Voltage (Note 6) I
O
=
5 mA, T
J
=
25˚C 60 mV
200 mV (max)
I
O
=
5 mA 300 mV (max)
I
O
=
500 mA, T
J
=
25˚C 350 mV
600 mV (max)
I
O
=
500 mA 700 mV (max)
Short Circuit Current V
IN
=
8V, R
L
=
1Ω 800 mA (min)
2A
3 A (max)
Ripple Rejection ƒ
RIPPLE
=
120 Hz, V
RIPPLE
=
1 Vrms, 60 dB (min)
I
O
=
50 mA
Output Impedance I
O
=
50 mAdc and 10 mArms
@
1 kHz 100 mΩ
Output Noise 10 Hz to 100 kHz, I
O
=
50 mA 1 mVrms
Long Term Stability 20 mV/1000 Hr
www.national.com 2
Electrical Characteristics (Continued)
V
IN
=
14.4V, C
O
=
10 µF, −40˚C ≤ T
J
≤ 125˚C, unless otherwise specified.
Parameter Conditions Typ Limit Units
(Note 4) (Note 5) (Limit)
REGULATOR OUTPUT
Maximum Operational Input
Voltage
Continuous 26 V (min)
Peak Transient Input Voltage V
O
≤ 7V, R
L
=
100Ω,t
f
=
100 ms 80 V (min)
Reverse DC Input Voltage V
O
≥ −0.6V, R
L
=
100Ω −18 V (min)
Reverse Transient Input Voltage t
r
=
1 ms, R
L
=
100Ω −50 V (min)
RESET OUTPUT
Threshold ∆V
O
Required for Reset Condition (Note 7) −80 mV (min)
−250 mV
−400 mV (max)
Output Low Voltage I
SINK
=
1.6 mA, V
IN
=
3.2V 0.15
0.4 V (max)
Internal Pull-Up Resistance 30 kΩ
Delay Time C
DELAY
=
10 nF (See Timing Curve) 19 ms
Minimum Operational V
IN
Delayed Reset Output ≤ 0.8V, 2.2 V
on Power Up I
SINK
=
1.6 mA, R
L
=
100Ω 3.2 V (min)
Minimum Operational V
O
Delay Reset Output ≤ 0.8V, 0.7 V
on Power Down I
SINK
=
10 µA, V
IN
=
0V
DELAY CAPACITOR PIN
Threshold Difference (∆V
DELAY
) Change in Delay Capacitor Voltage Required 3.5 V (min)
for Reset Output to Return High 3.75 V
4.1 V (max)
Charging Current (I
DELAY
) 1.0 µA (min)
2.0 µA
3.0 µA (max)
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
JMAX
, and θJA, and TA, and is limited by thermal shutdown. The maximum allowable power dissipation at
any ambient temperature is P
D
=
(T
JMAX–TA
)/θJA. If this dissipation is exceeded, the die temperature will rise above 150˚C and the device will go into thermal shut-
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
J
=
25˚C and represent the most likely parametric norm.
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
O
) has dropped 100 mV from the nominal value measured at V
IN
=
14.4V.
Note 7: The reset flag is set LOW when the output voltage has dropped an amount, ∆V
O
, from the nominal value measured at V
IN
=
14.4V.
Typical Performance Characteristics
Output Voltage
DS010759-15
Low Voltage Behavior
DS010759-16
Output at Voltage Extremes
DS010759-32
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