LT1033
NOT RECOMMENDED FOR NEW DESIGNS
Contact Linear Technology for Potential Replacement
3A Negative Adjustable
Regulator
DESCRIPTIO
U
Current Limit
6
35
LT1033 • G01
FEATURES
s
s
s
Guaranteed
1% Initial Voltage Tolerance
Guaranteed
0.015%/V Line Regulation
Guaranteed
0.02%/ W Thermal Regulation
PRECO DITIO I G
s
The LT
®
1033 negative adjustable regulator will deliver up
to 3A output current over an output voltage range of –1.2V
to –32V. Linear Technology has made significant
improvements in these regulators compared to previous
devices, such as better line and load regulation, and a
maximum output voltage error of 1%.
The LT1033 is easy to use and difficult to damage. Internal
current and power limiting as well as true thermal limiting
prevents device damage due to overloads or shorts, even
if the regulator is not fastened to a heat sink.
Maximum reliability is attained with Linear Technology’s
advanced processing techniques combined with a 100%
burn-in in the thermal limit mode. This assures that all
device protection circuits are working and eliminates field
failures experienced with other regulators that receive
only standard electrical testing.
, LTC and LT are registered trademarks of Linear Technology Corporation.
100% Thermal Limit Burn-in
APPLICATIO S
s
s
s
s
Adjustable Power Supplies
System Power Supplies
Precision Voltage/Current Regulators
On-Card Regulators
TYPICAL APPLICATIO
Negative 5V Regulator
R2
301Ω
2µF
TANT
ADJ
–V
IN
IN
LT1033
OUT
LT1033 • TA01
+
OUTPUT CURRENT (A)
U
UU
U
U
+
5
2µF
TANT
4
3
2
1
0
0
5
10
15
20
25
30
INPUT-OUTPUT DIFFERENTIAL (V)
R1
100Ω
–5V, 3A
1033fc
1
LT1033
ABSOLUTE
AXI U
RATI GS
(Note 1)
Storage Temperature Range
LT1033M
(OBSOLETE)
............................... –65°C to 150°C
LT1033C ..................................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec.) ........................ 300°C
Power Dissipation ....................................... Internally Limited
Input to Output Voltage Differential ................................. 35V
Operating Junction Temperature Range
LT1033M
(OBSOLETE)
............................... –55°C to 150°C
LT1033C ......................................................... 0°C to 125°C
PACKAGE/ORDER I FOR ATIO
BOTTOM VIEW
1
2
ADJ V
OUT
CASE IS
V
IN
K PACKAGE
4-LEAD TO-3 METAL CAN
T
JMAX
= 150°C,
θ
JA
= 35°C/W(MK)
T
JMAX
= 125°C,
θ
JA
= 35°C/W(CK)
CASE IS V
IN
T PACKAGE
3-LEAD PLASTIC TO-220
T
JMAX
= 125°C,
θ
JA
= 50°C/W
OBSOLETE PACKAGE
Consider the P or T Packages for Alternate Source
ORDER PART NUMBER
LT1033MK
LT1033CK
ORDER PART NUMBER
LT1033CT
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
(Note 2)
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
SYMBOL PARAMETER
V
REF
Reference Voltage
CONDITIONS
|V
IN
– V
OUT
| = 5V, I
OUT
= 5mA,
T
J
= 25°C
3V
≤
|V
IN
– V
OUT
|
≤
35V
5mA
≤
I
OUT
≤
I
MAX
, P
≤
P
MAX
∆V
OUT
∆I
OUT
Load Regulation
10mA
≤
I
OUT
≤
I
MAX
, (Note 3)
T
J
= 25°C,|V
OUT
|
≤
5V
T
J
= 25°C,|V
OUT
|
≥
5V
|V
OUT
|
≤
5V
|V
OUT
|
≥
5V
3V
≤
|V
IN
– V
OUT
|
≤
35V, (Note 2)
T
J
= 25°C
q
q
∆V
OUT
∆V
IN
Line Regulation
Ripple Rejection
V
OUT
= –10V, f = 120Hz
C
ADJ
= 0
C
ADJ
= 10µF
T
J
= 25°C, 10ms Pulse
Thermal Regulation
2
U
U
W
W W
U
W
FRONT VIEW
V
OUT
V
IN
ADJ
CASE IS V
IN
FRONT VIEW
V
OUT
V
IN
ADJ
P PACKAGE
3-LEAD PLASTIC TO-3P
T
JMAX
= 125°C,
θ
JA
= 35°C/W
ORDER PART NUMBER
LT1033CP
MIN
–1.238
–1.215
LT1033M
TYP
–1.250
–1.250
10
0.2
20
0.4
0.005
0.01
MAX
–1.262
–1.285
50
1.0
75
1.5
0.015
0.04
MIN
–1.238
–1.200
LT1033C
TYP
–1.250
–1.250
10
0.2
20
0.4
0.01
0.02
60
77
0.002
MAX
–1.262
–1.300
50
1.0
75
1.5
0.02
0.05
UNITS
V
V
mV
%
mV
%
%/V
%/V
dB
dB
q
q
56
70
66
80
0.002
0.02
66
0.02
%/W
1033fc
LT1033
ELECTRICAL CHARACTERISTICS
(Note 2)
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
SYMBOL PARAMETER
I
ADJ
∆I
ADJ
Adjust Pin Current
Adjust Pin Current Change
Minimum Load Current
I
SC
∆V
OUT
∆Temp
∆V
OUT
∆Time
e
n
θ
JC
Current Limit
Temperature Stability of
Output Voltage
Long Term Stability
RMS Output Noise
(% of V
OUT
)
Thermal Resistance
Junction to Case
10mA
≤
I
OUT
≤
I
MAX
3V
≤
|V
IN
– V
OUT
|
≤
35V
|V
IN
– V
OUT
|
≤
35V
|V
IN
– V
OUT
|
≤
10V
|V
IN
– V
OUT
|
≤
10V, (Note 3)
|V
IN
– V
OUT
| = 35V, T
J
= 25°C
T
MIN
≤
T
≤
T
MAX
T
A
= 125°C, 1000 Hours
T
A
= 25°C, 10Hz
≤
f
≤
10kHz
T Package
K Package
P Package
q
CONDITIONS
q
q
q
MIN
LT1033M
TYP
65
0.2
1.0
2.5
1.2
MAX
100
2
5
5.0
3.0
6
2.5
1.5
1.0
MIN
LT1033C
TYP
65
0.5
2
2.5
1.2
MAX
100
2
5
5.0
3.0
6
2.5
1.5
1.0
UNITS
µA
µA
µA
mA
mA
A
A
%
%
%
3
0.5
4.3
1.3
0.6
0.3
0.003
3
0.5
4.3
1.3
0.6
0.3
0.003
2.5
1.2
1.8
1.2
2.0
4.0
2.0
2.7
°C/W
°C/W
°C/W
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Unless otherwise indicated, these specifications apply:
|V
IN
– V
OUT
| = 5V; and I
OUT
= 5mA. Power dissipation is internally limited.
However, these specifications apply for power dissipation up to 30W.
See guaranteed minimum output current curve. I
MAX
= 3A.
Note 3:
Testing is done using a pulsed low duty cycle technique. See
thermal regulation specifications for output changes due to heating effects.
Load regulation is measured on the output pin at a point 1/8" below the
base of the package.
TYPICAL PERFOR A CE CHARACTERISTICS
Dropout Voltage
2.8
INPUT-OUTPUT DIFFERENTIAL (V)
2.6
REFERENCE VOLTAGE (V)
2.4
2.2
2.0
1.8
1.6
1.4
1.2
0.5
1.0
2.0
1.5
OUTPUT CURRENT (A)
2.5
3.0
T
J
= –55°C
CURRENT (mA)
T
J
= 25°C
T
J
= 150°C
U W
LT1033 • G02
Temperature Stability
1.27
1.8
1.6
Minimum Load Current
1.26
1.4
1.2
1.0
0.8
0.6
0.4
0.2
T
J
= 150°C
T
J
= –55°C
1.25
T
J
= 25°C
1.24
1.23
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
LT1033 • G03
0
0
10
30
20
INPUT-OUTPUT DIFFERENTIAL (V)
40
LT1033 • G04
1033fc
3
LT1033
APPLICATIONS INFORMATION
Output Voltage
The output voltage is determined by two external resis-
tors, R1 and R2 (see Figure 1). The exact formula for the
output voltage is:
R2
V
OUT
=
V
REF
1
+ +
I
ADJ
(
R2
)
R1
Where: V
REF
= Reference Voltage, I
ADJ
= Adjustment Pin
Current. In most applications, the second term is small
enough to be ignored, typically about 0.5% of V
OUT
. In
more critical applications, the exact formula should be
used, with I
ADJ
equal to 65µA. Solving for R2 yields:
R2
=
V
OUT
– V
REF
V
REF
– I
ADJ
R1
which must be absorbed, is 5mA for the LT1033. If input-
output voltage differential is less than 10V, the operating
current that must be absorbed drops to 3mA.
Capacitors and Protection Diodes
An output capacitor, C3, is required to provide proper
frequency compensation of the regulator feedback loop.
A 2µF or larger solid tantalum capacitor is generally
sufficient for this purpose if the 1MHz impedance of the
capacitor is 1Ω or less. High Q capacitors, such as Mylar,
are not recommended because their extremely low ESR
(effective series resistance) can drastically reduce phase
margin. When these types of capacitors must be used
because of other considerations, add a 0.5Ω carbon
resistor in series with 1µF. Aluminum electrolytic capaci-
tors may be used, but the minimum value should be 25µF
to ensure a low impedance at 1MHz. The output capacitor
should be located within a few inches of the regulator to
keep lead impedance to a minimum. The following caution
should be noted: if the output voltage is greater than 6V
and an output capacitor greater than 20µF has been used,
it is possible to damage the regulator if the input voltage
becomes shorted, due to the output capacitor discharging
into the regulator. This can be prevented by using diode D1
(see Figure 2) between the input and the output.
The input capacitor, C2, is only required if the regulator is
more than 4 inches from the raw supply filter capacitor.
Bypassing the Adjustment Pin
The adjustment pin of the LT1033 may be bypassed with
a capacitor to ground, C1, to reduce output ripple, noise,
and impedance. These parameters scale directly with
output voltage if the adjustment pin is not bypassed. A
bypass capacitor reduces ripple, noise and impedance to
that of a 1.25V regulator. In a 15V regulator for example,
these parameters are improved by 15V/1.25V = 12 to 1.
This improvement holds only for those frequencies where
the impedance of the bypass capacitor is less than R1. Ten
microfarads is generally sufficient for 60Hz power line
applications where the ripple frequency is 120Hz, since
X
C
= 130Ω. The capacitor should have a voltage rating at
least as high as the output voltage of the regulator. Values
1033fc
Smaller values of R1 and R2 will reduce the influence of
I
ADJ
on the output voltage, but the no-load current drain on
the regulator will be increased. Typical values for R1 are
between 100Ω and 300Ω, giving 12.5mA and 4.2mA
no-load current respectively. There is an additional con-
sideration in selecting R1, the minimum load current
specification of the regulator. The operating current of the
LT1033 flows from input to output. If this current is not
absorbed by the load, the output of the regulator will rise
above the regulated value. The current drawn by R1 and R2
is normally high enough to absorb the current, but care
must be taken in no-load situations where R1 and R2 have
high values. The maximum value for the operating current,
+
+
C2
5µF
ADJ
–V
IN
V
IN
LT1033
LT1033 • F01
C1
10µF
R2
I
ADJ
V
REF
R1
–V
OUT
+
C3
2µF
V
OUT
EXAMPLE:
1. A PRECISION 10V REGULATOR TO SUPPLY UP TO 3A LOAD CURRENT.
A. SELECT R1 = 100Ω TO MINIMIZE EFFECT OF I
ADJ
B. CALCULATE R2 =
V
OUT
– V
REF
10V – 1.25V
=
= 704Ω
V
REF
1.25V
– 65µA
– I
ADJ
100Ω
R1
Figure 1
U
W
U
U
5
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