NSC LM2925T Datasheet
LM2925
Low Dropout Regulator with Delayed Reset
General Description
The LM2925 features a low dropout, high current regulator.
Also included on-chip is a reset function with an externally
set delay time. Upon power up, or after the detection of any
error in the regulated output, the reset pin remains in the active low state for thedurationofthedelay. Typesoferrors detected include any that cause the output to become unregulated: low input voltage, thermal shutdown, short circuit,
input transients, etc. No external pull-up resistor is necessary.The current charging the delay capacitor is very low, allowing long delay times.
Designed primarily for automotive applications, the LM2925
and all regulated circuitry are protected from reverse battery
installations or two-battery jumps. During line transients,
such as a load dump (60V) when the input voltage to the
regulator can momentarily exceed the specified maximum
operating voltage, the 0.75A regulator will automatically shut
down to protect both internal circuits and the load. The
Typical Application Circuit
LM2925 cannot be harmed by temporary mirror-image insertion. Familiar regulator features such as short circuit and
thermal overload protection are also provided.
Features
n 5V, 750 mA output
n Externally set delay for reset
n Input-output differential less than 0.6V at 0.5A
n Reverse battery protection
n 60V load dump protection
n −50V reverse transient protection
n Short circuit protection
n Internal thermal overload protection
n Available in plastic TO-220
n Long delay times available
+
n P
Product Enhancement tested
Connection Diagram
LM2925 Low Dropout Regulator with Delayed Reset
April 1998
*
Required if regulator is located far from power supply filter.
**
C
must be at least 10 µF to maintain stability. May be increased
OUT
without bound to maintain regulation during transients. Locate as close as
possible to the regulator. This capacitor must be rated over the same
operating temperature range as the regulator. The equivalent series
resistance (ESR) of this capacitor is critical; see curve.
FIGURE 1. Test and Application Circuit
DS005268-1
TO-220 5-Lead
DS005268-2
Order Number LM2925T
See NS Package Number T05A
© 1998 National Semiconductor Corporation DS005268 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
Operating Range 26V
Overvoltage Protection 60V
V
OUT
Electrical Characteristics
=
V
14V, C2=10 µf, I
IN
=
O
500 mA, T
=
25˚C (Note 4) (unless otherwise specified)
J
Internal Power Dissipation (Note 2) Internally Limited
Operating Temperature Range −40˚C to + 125˚C
Maximum Junction Temperature 150˚C
Storage Temperature Range −65˚C to + 150˚C
Lead Temperature
(Soldering, 10 seconds) 260˚C
ESD rating is to be determined
Parameter Conditions Min Typ Max Units
(Note 3)
Output Voltage 6V≤ V
Line Regulation 9V ≤ V
Load Regulation 5 mA ≤ I
Output Impedance 500 mA
≤ 26V, IO≤ 500 mA, V
IN
−40˚C≤ T
6V ≤ V
≤ +125˚C 4.75 5.00 5.25
J
≤ 16V, I
IN
≤ 26V, I
IN
O
DC
=
5 mA 4 25 mV
O
=
5mA 10 50 mV
O
≤ 500 mA 10 50 mV
and 10 mArms, 200 mΩ
100 Hz-10 kHz
Quiescent Current I
≤ 10 mA 3 mA
O
=
I
500 mA 40 100 mA
O
=
I
750 mA 90 mA
O
Output Noise Voltage 10 Hz-100 kHz 100 µVrms
Long Term Stability 20 mV/1000 hr
Ripple Rejection f
Dropout Voltage I
=
120 Hz 66 dB
o
=
500 mA 0.45 0.6 V
O
=
I
750 mA 0.82 V
O
Current Limit 0.75 1.2 A
Maximum Operational 26 31 V
Input Voltage
Maximum Line Transient V
Reverse Polarity Input V
≤ 5.5V 60 70 V
O
≥ − 0.6V, 10Ω Load −15 −30 V
O
Voltage, DC
Reverse Polarity Input 1%Duty Cycle, τ≤100 ms, −50 −80 V
Voltage, Transient 10Ω Load
Reset Output
Electrical Characteristics
=
V
14V, C3=0.1 µF, T
IN
Parameter Conditions Min Typ Max Units
Reset Voltage
Output Low I
Output High I
Reset Internal Pull-up Resistor 30 kΩ
Reset Output Current Limit V
V
Threshold 4.5 V
OUT
Delay Time C
www.national.com 2
=
25˚C (Note 4) (unless otherwise specified)
A
=
1.6 mA, V
SINK
SOURCE
RESET
=
.005 µF 12 ms
3
=
C
0.1 µF 150 250 300 ms
3
=
C
4.7 µF tantalum 12 s
3
IN
=
0 4.5 5.0 5.5 V
=
1.2 V 5 mA
(Note 3)
=
35V 0.3 0.6 V
Reset Output
Electrical Characteristics
=
V
14V, C3=0.1 µF, T
IN
Parameter Conditions Min Typ Max Units
Delay Current Pin 4 1.2 1.95 2.5 µA
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating Conditions.
Note 2: Thermal resistance without a heat sink for junction to case temperature is 3˚C/W (TO-220). Thermal resistance for TO-220 case to ambient temperature is
50˚C/W.
Note 3: These parameters are guaranteed and 100%production tested.
Note 4: To ensure constant junction temperature, low duty cycle pulse testing is used.
=
25˚C (Note 4) (unless otherwise specified)
A
(Continued)
(Note 3)
Typical Circuit Waveforms
DS005268-3
FIGURE 2.
Typical Performance Characteristics
Reset Voltage
DS005268-4
Reset Voltage
Delay Time
DS005268-5
3 www.national.com
DS005268-6
Loading...