TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
SOP-8
Pin Definition:
1. Output
8. Input
2. Ground
7. Ground
3. Ground
6. Ground
4. Adj
5. Inhibit
General Description
The TS2938 series of fixed-voltage monolithic micro-power voltage regulators is designed for a wide range of
applications. This device excellent choice of use in battery-power application. Furthermore, the quiescent current
increases on slightly at dropout, which prolongs battery life.
This series of fixed-voltage regulators features very low ground current (200uA Typ.), very low drop output voltage
(Typ. 60mV at light load and 600mV at 500mA) and output inhibit control. This includes a tight initial tolerance of 2%,
extremely good line regulation of 0.05% typ., and very low output temperature coefficient.
Features
●
●
●
●
●
●
●
●
●
●
Dropout voltage typically 0.5V @Io=500mA
Output current up to 500mA
Logic Control Electronic Shutdown
Output voltage trimmed before assembly
-18V Reverse peak voltage
+30V Input over voltage protection
+60V Transient peak voltage
Low Quiescent Current 100uA (Typ.) (On Mode)
Internal current limit
Thermal shutdown protection
Block Diagram
Ordering Information
Part No.
Package
Packing
TS2938CSxx RL
SOP-8
2.5Kpcs / 13” Reel
Note: Where
xx
denotes voltage option, available are
12=
12V
10=
10V
80=
8.0V
50=
5.0V
33=
3.3V
Leave blank for adjustable voltage
Contact factory for additional voltage options.
1/7
Version: A07
TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
Absolute Maximum Rating
(Note 1)
Parameter
Input Supply Voltage (Note 2)
Operation Input Supply Voltage
Power Dissipation (Note 3)
Operating Junction Temperature Range
Storage Temperature Range
Symbol
V
IN
V
OPR
P
D
T
J
T
STG
Limit
-18 ~ +60
26
Internally Limited
-40 ~ + 125
-65 ~ +150
Unit
V
V
W
o
o
C
C
Electrical Characteristics
( V
IN
=V
OUT
+1V, I
L
=5mA, C
O
=10uF, T
A
=25
o
C
, unless otherwise noted)
Parameter
Output Voltage
Reference Voltage (Adjustable)
Output Voltage Temperature Coefficient
Line Regulation
Load Regulation
Dropout Voltage (Note 4)
Conditions
T
A
=25
C
T
A
=25~85
o
C
T
A
=25
o
C
Vo+1V
≤
V
IN
≤
26V
5mA
≤
I
L
≤
500mA
I
L
=100mA
I
L
=300mA
I
L
=500mA
I
L
=100uA
I
L
=300mA
I
L
=500mA
V
OUT
=0
C
L
=2.2uF
C
L
=3.3uF
C
L
=33uF
Ratio
Low (Regulator ON)
High (Regulator OFF)
Vinhibit = 2.4V
Vinhibit = 26V
Vinhibit≤2V, Vin≤26V
Vout=0V
o
Min
0.980|Vo|
0.960|Vo|
1.21
--
--
--
--
--
--
--
--
--
--
--
--
--
60
--
2.0
--
--
--
Typ
V
OUT
1.235
50
0.05
0.2
100
300
500
200
12
25
0.9
500
350
120
--
1.3
--
30
450
--
Max
1.020|Vo|
1.040|Vo|
1.26
150
0.5
1.0
200
400
600
300
20
50
1.3
--
--
--
--
0.7
--
50
600
200
Unit
V
V
V
o
ppm/ C
%
%
mV
uA
mA
mA
A
uVrms
dB
Quiescent Current (Note 5)
Short Circuit Current (Note 6)
Output Noise,
10Hz to 100KHz, I
L
=10mA
Ripple Rejection
Shutdown Input
Input Logic Voltage
Shutdown Pin Input Current
Regulator Output Current in Shutdown
V
uA
Thermal Performance
Condition
Thermal Resistance Junction to Case
Typ
20
Unit
o
C/W
2/7
Version: A07
TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
Electrical Characteristics (Continue)
Note 1: Absolute Maximum Rating is limits beyond which damage to the device may occur. For guaranteed
Specifications and test conditions see the Electrical Characteristics.
Note 2: Maximum positive supply voltage of 60V must be limited duration (<100mS) and duty cycle (<1%).
Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, Tj, the junction
to ambient thermal resistance,
θja,
and the ambient temperature, Ta. Exceeding the maximum allowable
power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. The
effective value of
θja
can be reduced by using a heatsink.
Note 4: Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its
nominal value measured at 1V differential.
Note 5: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the
ground pin current and output load current.
Note 6: Output current will decrease with increasing temperature, but it will be not dropped below 500mA at the
maximum specified temperature.
Application Circuit
Fixed Output Voltage Type
Adjustable Output Voltage Type
3/7
Version: A07
TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
Application Information
Application
The TS2938 series is a high performance with low dropout voltage regulator suitable for moderate to high current
and voltage regulator application. Its 500Mv (typ) dropout voltage at full load and over temperature makes it
especially valuable in battery power systems and as high efficiency noise filters in post regulator applications. Unlike
normal NPN transistor design, where the base to emitter voltage drop and collector to emitter saturation voltage limit
the minimum dropout voltage, dropout performance of the PNP output of these devices is limited only by low Vce
saturation voltage.
The TS2938 series is fully protected from damage due to fault conditions. Linear current limiting is provided. Output
current during overload conditions is constant. Thermal shutdown the device when the die temperature exceeds the
maximum safe operating temperature. Transient protection allows device survival even when the input voltage
spikes above and below nominal. The output structure of these regulators allows voltages in excess of the desired
output voltage to be applied without reverse current flow.
Output Capacitor
The TS2938 series requires an output capacitor to maintain stability and improve transient response. Proper
capacitor selection is important to ensure proper operation. The output capacitor selection is dependent upon the
ESR of the output capacitor the maintain stability. When the output capacitor is 6.8uF or greater, the output capacitor
should have an ESR less than 2 ohm. This will improve transient response as well as promoted stability. Ultra low
ESR capacitors (<100mohm), such as ceramic chip capacitors may promote instability. These very low ESR levels
may cause an oscillation and/or under damped transient response. A low ESR solid tantalum capacitor works
extremely well and provide good transient response and stability over temperature. Aluminum electrolytic can also be
used, as long as the ESR of the capacitor is <2ohm. The value of the output capacitor can be increased without limit.
Higher capacitance values help to improved transient response and ripple rejection and reduce output noise.
Minimum Load Current
The TS2938 series is specified between finite loads. If the output current is too small leakage currents dominate and
the output voltage rises. A 5mA minimum load current is necessary for proper regulation.
Input Capacitor
An input capacitor of 1uF or greater is recommended when the device is more that 4 inches away from the bulk AC
supply capacitance or when the supply is a battery. Small and surface mount ceramic chip capacitors can be used
for bypassing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further
improving the integrity of the output voltage.
Adjustable Regulator Design
The adjustable regulator versions is allow to programming the output voltage anywhere between 1.25 and the 26V
maximum operating rating of the family.
Two resistors are used. Resistors can be quite large up to 1MΩ, because of the very high input impedance and low
bias current of the sense comparator, the resistor values are calculated by:
4/7
Version: A07
TS2938
500mA Ultra Low Dropout Voltage Regulator
with Inhibit Function
Application Information (Continue)
Thermal Characteristics
A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the
application. Under all possible operating conditions, the junction temperature must be within the range specified
under absolute maximum ratings. To determine if the heatsink is required, the power dissipated by the regulator, P
D
must be calculated.
The below formula shows the voltages and currents for calculating the P
D
in the regulator:
I
IN
= I
L
/ I
G
P
D
= (V
IN
-V
OUT
) * I
L
+ (V
IN
) * I
G
Ex. P
D
= (3.3V-2.5V) * 0.5A + 3.3V * 11mA
= 400mW + 36mW
= 436mW
The next parameter which must be calculated the maximum allowable temperature rise.
T
R
(max) is calculated by the using to formula:
T
R
(max) = T
J
(max) – T
A
(max)
o
Where: T
J
(max) is the maximum allowable junction temperature, which is 125 C for commercial grade parts. T
A
(max)
is the maximum ambient temperature which will be encountered in the application.
Using the calculated values for T
A
(max) and P
D
, the maximum allowable value for the junction to ambient thermal
resistance,
θ
JA
, can now be found:
θ
JA
= T
R
(max) / P
D
Inhibit Input
TS2938 feature an active-low (Inhibit) input that allows ON/OFF control of the regulator. The Inhibit input has
TTL/CMOS compatible thresholds for simple interfacing with logic interfacing. Inhibit should be directly tied to
Ground or keep open (not connected).
5/7
Version: A07
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