TS2938/A
500mA Ultra Low Dropout Fixed Voltage Regulator with Inhibit
Pin assignment:
1. Input
2. Inhibit
3. Gnd
4. N/C
5. Output
Pin assignment:
1. Output 8. Input
2. Gnd
7. Gnd
3. Gnd
6. Gnd
4. N/C
5. Inhibit
Low Dropout Voltage 0.6V max.
Logic Inhibit Control
General Description
T
he TS2938/A 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 (100uA 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 1% (TS2938A)
and 2% (TS2938), extremely good line regulation of 0.05% typ., and very low output temperature coefficient.
This series is offered in 5-pin of TO-252-5L and 8-pin SOP-8 package.
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.
TS2938CP5xx
TS2938ACP5xx
TS2938CSxx
-20 ~ +85 C
SOP-8
o
Operation Temp.
(Ambient)
Package
TO-252-5L
TS2938ACSxx
Note: Where
xx
denotes voltage option, available are
8.0V, 5.0V, 3.3V and 2.5V. Contact factory for
additional voltage options.
Absolute Maximum Rating
(Note 1)
Input Supply Voltage (Note 2)
Operation Input Supply Voltage
Power Dissipation (Note 3)
Operating Junction Temperature Range
Storage Temperature Range
Lead Soldering Temperature (260
o
C)
TO-252 / SOP-8 Package
5
S
Vin
Vin (operate)
P
D
T
J
T
STG
-18 ~ +60
26
Internally Limited
-40 ~ +125
-65 ~ +150
V
V
W
o
o
C
C
TS2938/A
1-5
2004/09 rev. A
Electrical Characteristics
Vin = Vout + 1V, I
L
= 5mA, C
o
= 6.8uF, Ta = 25
o
C, Vinhibit = 0V, unless otherwise specified.
Parameter
Output Voltage
Output Voltage
Input Supply Voltage
Output Voltage Temp. Coefficient
Line Regulation
Load Regulation
Dropout Voltage (Note 4)
o
Conditions
Ta = 25 C
Ta = -25 ~ 85
o
C
TS2938A
TS2938
TS2938A
TS2938
Min
0.990|Vo|
0.980|Vo|
0.980|Vo|
0.960|Vo|
--
--
Typ
8.0 / 5.0
3.3 / 2.5
Max
1.010|Vo|
1.020|Vo|
1.020|Vo|
1.040|Vo|
Unit
v
V
V
V
ppm/
o
C
%
%
mV
uA
mA
A
uVrms
dB
--
50
0.05
0.2
100
300
500
100
12
25
0.9
500
350
120
--
26
150
0.5
1.0
200
400
600
200
20
50
1.3
--
--
--
--
Vo+1V
≤
Vin
≤
26V
5mA
≤
I
L
≤
500mA
I
L
=100mA
I
L
=300mA
I
L
=500mA
--
--
--
--
--
--
--
--
--
--
--
--
60
Quiescent Current (Note 5)
I
L
=100uA
I
L
=300mA
I
L
=500mA
Short Circuit Current (Note 6)
Output Noise,
10Hz to 100KHz, I
L
=10mA
Ripple Rejection Ratio
Shutdown Input
Input Logic Voltage
Shutdown Pin Input Current
Regulator Output Current in
Shutdown
Vout=0
C
L
=2.2uF
C
L
=3.3uF
C
L
=33uF
Io=350mA, f=120Hz,
Co=100uF, Vin=Vo+3V+2Vpp
Low (Regulator ON)
High (Regulator OFF)
Vinhibit = 2.4V
Vinhibit = 26V
Vinhibit
≤
2V, Vin
≤
26V,
Vout = 0V
--
2.0
--
--
--
1.3
--
30
450
--
0.7
--
50
600
200
V
uA
Thermal Performance
Condition
Thermal Resistance
Junction to Ambient
TO-252
Package type
Typ
150
Unit
o
C/W
SOP-8
170
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.
TS2938/A
2-5
2004/09 rev. A
Application Information
The TS2938/A 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/A 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.
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/A 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.
Typical Application Circuit
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:
Iin = I
L
/ I
G
P
D
= (Vin-Vout) * I
L
+ (Vin) * I
G
Ex. P
D
= (3.3V-2.5V) * 0.5A + 3.3V * 11mA
= 400mW + 36mW
= 436mW
Remark: I
L
is output load current,
I
G
is ground current.
Vin is input voltage
Vout is output voltage
Output Capacitor
The TS2938/A 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
TS2938/A
3-5
2004/09 rev. A
Application Information (continued)
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)
Where: T
J
(max) is the maximum allowable junction
o
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
R
(max) and P
D
, the
maximum allowable value for the junction to ambient
thermal resistance,
θja
, can now be found:
θja
= T
R
(max) / P
D
Inhibit Input
TS2938/A 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).
IMPORTANT:
if the maximum allowable value for is found to be
≥
60
o
C/W for the TO-220 package,
≥80
o
C/W for the
o
TO-263 package,
≥150
C/W for the TO-252 package,
o
or
≥170
C/W for the SOT-223 package, no heatsink is
needed since the package alone will dissipate enough
heat to satisfy these requirements. If the calculated
value for
θja
falls below these limits, a heatsink is
required.
TS2938/A
4-5
2004/09 rev. A
SOP-8 Mechanical Drawing
A
DIM
SOP-8 DIMENSION
MILLIMETERS
INCHES
MIN
MAX
MIN
MAX
4.80
5.00
0.189
0.196
3.80
4.00
0.150
0.157
1.35
1.75
0.054
0.068
0.35
0.49
0.014
0.019
0.40
1.25
0.016
0.049
1.27 (typ)
0.05 (typ)
0.10
0.25
0.004
0.009
o
o
o
0
7
0
7
o
5.80
6.20
0.229
0.244
0.25
0.50
0.010
0.019
16
9
B
P
1
8
G
C
D
K
M
R
F
A
B
C
D
F
G
K
M
P
R
TO-252-5L Mechanical Drawing
DIM
A
B
C
D
E
F
G
H
I
J
TO-252-5L DIMENSION
MILLIMETERS
INCHES
MIN
6.350
9.250
0.460
2.560
2.190
0.460
1.400
0.460
5.340
1.520
MAX
6.730
10.400
0.640
2.670
2.380
0.570
1.780
0.570
5.550
2.030
MIN
0.2509
0.364
0.018
0.101
0.086
0.018
0.055
0.018
0.210
0.060
MAX
0.265
0.409
0.025
0.105
0.094
0.022
0.070
0.022
0.219
0.080
TS2938/A
5-5
2004/09 rev. A
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