PJ2931

Ultra Low Dropout Voltage Regulator

1-6

2002/01.rev.A

He PJ2931 voltage regulator features a very low quiescent current of 1mA or less when supplying 10mA loads. This unique
characteristic and the extremely low in-put-output differential required for proper regulation (0.2V for output currents of

10mA) make the PJ2931 the ideal regulator for standby power systems. Applications include memory standby circuits, CMOS
and other low power processor power supplies as well as systems demanding as much as 100mA of output current.
Designed originally for automotive applications, the PJ2931 and all regulated circuitry are protected from reverse battery
installations or 2 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 regulator will automatically shut down to protect both internal
circuits and the load. The PJ2931 can not be harmed by temporary mirror-image insertion. Familiar regulator features such as
short circuit and thermal overload protection are also provided.
Fixed output of 5V is available in the popular TO-92 and SOT-89 package. An adjustable output version, with on/off switch,
is available in SOP-8 package.

Very low quiescent current

Output current in excess of 100mA

Input-Output differential less than 0.6V

Reverse battery protection

Unregulated DC input can withstand +60V positive transients

and -20V reverse battery

Short circuit protection

Internal thermal overload protection

Available as adjustable with TTL compatible switch

100% electrical burn-in in thermal limit

Available in plastic SOP-8, TO-92, SOT-89 package

Input Supply Voltage

+26V

Internal Power Dissipation (Note 1)

Internally Limited

Operating Temperature Range

-20 to +85

Maximum Junction Temperature

125

Storage Temperature Range

-40 to +150

Lead Temp.(Soldering, 10 seconds)

210

FEATURES

Device Operating

Temperature

Package

PJ2931CT-xx TO-92
PJ2931CY-xx SOT-89
PJ2931CS-xx
PJ2931CS-Adj

-20 ~ +85

SOP-8

xx = Output Voltage (2.85V, 3.3V, 5.0V)

ORDER INFORMATION

TO-92 SOT-89

ABSOLUTE MAXIMUM RATINGS

Pin : 1. Output
2. Ground

3. Input

Pin : 1. Output 5. On/Off
2. Ground 6. Ground

3. Ground 7. Ground
4. By passb/Adj 8. Input

SOP-8

PJ2931

Low Dropout Voltage Regulator

2-6

2002/01.rev.A

PJ2931 Units

Parameter

Conditions

Min. Typ. Max.

-20 Tj

Full operating temperature

0.985|Vo|

0.98|Vo|

Vo 1.015|Vo|

1.02|Vo|

Output Voltage (Fix Type)

Io =100uA ~ 100mA, Tj Tj max

0.975|Vo|

1.025|Vo|

Input Supply Voltage

Line Regulation

13VV

16V

Load Regulation

5mAIo100mA

Dropout Voltage

Io=10mA
Io=100mA

300

200
600

Ground Current

Io=100uA
Io=10mA
Io=100mA

0.1

0.9

0.15

1.5

Current Linit

Vout=0

160

200

Output Noise Voltage

10Hz-100KHz, C

OUT

=100�F

500

uVRMS

Ripple Rejection Ratio

Io =10mA, fo=120Hz

Adjustable Type Only

Vout = 3V, Io100mA, R1=27K

1.21

1.235

1.26

Reference Voltage

Full Operation Temperature

1.185

1.285

Feedback Pin Bias Current

Feedback Pin Bias Current Temperature
Coefficient

nA/

Reference Voltage Temperature
Cofficient

Ppm/

Shutdown Input

Input Logic Voltage

Low (Regulator ON)
High (Regulator OFF)

1.3 0.7 V

Shutdown Pin Input Current

Vs=2.4V
Vs=26V

450

600

Regulator Output Current in Shutdown

Note 1: Output or reference voltage temp. coefficients defined as the worst case voltage change divided by the total temp. range.
Note 2: Regulations is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output

voltage due to heating effects is covered under the specification for thermal regulation.

Note 3: Line regulation is tested at 125for I

=1mA, For I

=100A and T

=125.

Note 4: Dropout voltage is defined as the input to output differential at which the output voltage drops 2 below it's nominal

value measured at 1V differential.

Note 5: Ground pin current is the regulator quiescent current. The total current drawn form the source is the sum of the ground
pin

current and output load current.

Note 6: Thermal regulation is the change in output voltage at a time T after a change in power dissipation, excluding load or line

regulation effects. Specifications are for a 50mA load pulse (1.25W) for T=10ms.

Note 7: Vref Vout (Vin-1V), 2.3VVin26V, 100AI

100mA, T

JMAX

Note 8: Vshutdown 2V, Vin26V, Vout=0V

ELECTRICAL CHARACTERISTICS

=14V,Io=10mA, T

=25(Note 1), Co=100F(unless otherwise specified)

PJ2931

Low Dropout Voltage Regulator

3-6

2002/01.rev.A

Application Hints
One of the distinguishing factors of the PJ2931 series
regulators is the requirement of an output capacitor for device
stability. The value required varies greatly depending upon
the application circuit and other factors. Thus some comments
on the characteristics of both capacitors and the regulator are
in order.
High frequency characteristics of electrolytic capacitors
depend greatly on the type and even the manufacturer. As a
result, a value of capacitance that works well with the PJ2931
for one brand or type may not necessary be sufficient with an
electrolytic of different origin. Sometimes actual bench
testing, as described later, will be the only means to determine
the proper capacitor and value. Experience has shown that, as
a rule of thumb, the more expensive and higher quality
electrolytic generally allows a smaller value for regulator
stability. As an example, while a high-quality 100

�F

aluminum electrolytic covers all general application circuits,
similar stability can be obtained with a tantalum electrolytic of
only 47

�F. This factor of two can generally be applied to any

special application circuit also.
Another critical characteristic of electrolytic is their
performance over temperature. While the PJ2931 is designed
to operate to -20, the same is not always true with all
electrolytic(hot is generally not a problem). The electrolyte in
many aluminum types will freeze around -250, reducing
their effective value to zero. Since the capacitance is needed
for regulator stability, the natural result is oscillation (and lots
of it) at the regulator output. For all application circuits where
cold operation is necessary, the output capacitor must be rated
to operate at the minimum temperature. By coincidence,
worst-case stability for the PJ2931 also occurs at minimum
temperatures. As a result, in applications where the regulator
junction temperature will never be less than 25, the output
capacitor can be reduced approximately by a factor of two
over the value needed for the entire temperature range. To
continue our example with the tantalum electrolytic, a value
of only 22

�F would probably thus suffice. For high-quality

aluminum, 47

�F would be adequate in such an application.

Another regulator characteristic that is noteworthy is that
stability decreases with higher output currents. This sensible
fact has important connotations. In many applications, the
PJ2931 is operated at only a few milliamps of output current
or less. In such a circuit, the output capacitor can be further
reduced in value. As a rough estimation, a circuit that is
required to deliver a maximum of 10mA of output current
from the regulator would need an output capacitor of only half
the value compared to the same regulator required to deliver
the full output current of 100mA. If the example of the
tantalum capacitor in the circuit rated at 25 junction
temperature and above were continued to include a maximum
of 10 mA of output current, then the 22

�F output capacitor

could be reduced to only 10

�F.

In the case of the PJ2931CS adjustable regulator in SOP-8
package, the minimum value of output capacitance is a
function of the output voltage. As a general rule, the value
decreases with higher output voltages, since internal loop gain
is reduced.
At this point, the procedure for bench testing the minimum
value of an output capacitor in a special application circuit
should be clear. Since worst-case occurs at minimum
operating temperatures and maximum operating currents, the
entire circuit, including the electrolytic, should be cooled to
the minimum temperature. The input voltage to the regulator
should be maintained at 0.6V above the output to keep
internal power dissipation and die heating to a minimum.
Worst-case occurs just after input power is applied and before
the die has had a chance to heat up. Once the minimum value
of capacitance has been found for the brand and type of
electrolytic in question, the value should be doubled for actual
use to account for production variations both in the capacitor
and the regulator. (All the values in this section and the
remainder of the data sheet were determined in this fashion.)
Definition of Terms
Dropout Voltage: The input-output voltage differential at
which the circuit ceases to regulate against further reduction
in input voltage. Measured when the output voltage has
dropped 100 mV from the nominal value obtained at 14V
input, dropout voltage is dependent upon load current and
junction temperature.
Input Voltage: The DC voltage applied to the input terminals
with respect to ground.
Input-Output Differential: The voltage difference between
the unregulated input voltage and the regulated output voltage
for which the regulator will operate.
Line Regulation: The change in output voltage for a change
input voltage. The measurement is made under conditions of
low dissipation or by using pulse techniques such that the
average chip temperature is not significantly affected.
Load Regulation: The change in output voltage for a change
in load current at constant chip temperature.
Output Noise Voltage: The rms AC voltage at the output,
with constant load and no input ripple, measured over a
specified frequency range.
Quiescent Current: That part of the positive input current
that does not contribute to the positive load current. The
regulator ground lead current.
Ripple Rejection: The ratio of the peak-to-peak input ripple
voltage to the peak-to-peak output ripple voltage.
Temperature Stability of Output Voltage: The percentage
change in output voltage for a thermal variation from room
temperature true to either temperature extreme.

Электронный компонент: PJ2931CS-2.85V