3A Low Dropout Positive Adjustable Regulator
Description
The GS1085 is a low dropout three terminal regulator with
3A output current capability. The output voltage is
adjustable with the use of a resistor divider. For fixed output
voltage versions, the output voltage is internally set at
1.8V, 2.5V, or 3.3V. Dropout is guaranteed at a maximum
of 1.3V at maximum output current. Its low dropout voltage
and fast transient response make it ideal for low voltage
microprocessor applications. Internal current and thermal
limiting provides protection against any overload condition
that would create excessive junction temperatures.
Applications
• Post Regulator for Switching Supply
• Microprocessor Power Supplies
• Constant-Current Regulators
• Motherboard I/O Power Supplies
Mechanical Data
Case: TO-220AB, TO-263AB (D2PAK),
TO-252 (DPAK)
High temperature soldering guaranteed:
260°C/10 seconds at terminals
Case outlines are on the back page
+
+--
For
fixed
voltage
device
Thermal
Limit
Current
Amp
Current
Limit
GM
VOUT
VIN
ADJ GND
VREF
1.25V
55µA
Functional Block Diagram
Features
• Dropout Voltage 1.3V at 3A Output Current
• Fast Transient Response
• Line Regulation typically at 0.015%
• Load Regulation typically at 0.1%
• Internal thermal and current limiting
Adjustable Output Voltage or Fixed 1.8V, 2.5V, 3.3V
• Standard 3-Pin Power Packages
TO-220AB TO-263AB
(D2Pak)
GS1085CT GS1085CMGS1085CE
TO-252
(DPak)
1
2
3
1
23
1
23
Pin Definition
1. Adjust/Gnd.
2. Vout (tab)
3. Vin
GS1085
Vishay Siliconix
Document Number 74821 www.vishay.com
07-Mar-05 1
Maximum Ratings and Thermal Characteristics (TA= 25°C unless otherwise noted)
Parameter Symbol Value Unit
Vin Pin to ADJ/GND Pin Vin 7 V
Thermal Resistance – Junction to Case
TO-220AB 3.0
TO-252 RθJC 8.0 °C/W
TO-263AB 3.0
Operating Junction Temperature Range TJ0 to +125 °C
Storage Temperature Range Tstg 65 to 150 °C
Electrical Characteristics(1) TJ= 25°C (2), VIN = 5V, Io= 10mA unless otherwise noted.
Parameter Symbol Test Conditions Min Typ Max Unit
Reference Voltage VREF TJ= 25°C 1.225 1.250 1.275 V
0°C TJ125°C 1.213 1.250 1.288
GS1085-1.8 VIN = 5V 1.76 1.8 1.84
Output Voltage VOUT GS1085-2.5 VIN = 5V 2.45 2.5 2.55 V
GS1085-3.3 VIN = 7V 3.23 3.3 3.37
GS1085 0.98VNVN1.02VN
0°C TJ125°C
2.75V VIN 7V
Line Regulation REGline TJ= 25°C 0.015 0.2 % VO
0°C TJ125°C 0.035 0.2
10mA Io3A
Load Regulation REGload TJ= 25°C 0.1 0.3 % VO
0°C TJ125°C 0.2 0.4
0°C TJ125°C
Dropout Voltage VDROP Io= 3A 1.2 1.3 V
Io= 2A 1.1 1.2
Io= 1A 1.0 1.1
Output Current Io0°C TJ125°C 3.0 4.0 A
2.75 Vin 7V
Adjust Pin Current Iadj 10mA Io3A 55 120 µA
0°C TJ125°C
2.75 Vin 7V
Adjust Pin Current Change Iadj 10mA Io3A 0.2 5 µA
0°C TJ125°C
Temperature Stability TSIo= 0.5A 0.5 %VO
0°C TJ125°C
Minimum Load Current ILMIN 0°C TJ125°C 5 10 mA
Adjustable Version
GS1085
Vishay Siliconix
www.vishay.com Document Number 74821
207-Mar-05
Electrical Characteristics(con’t.)(1) TJ= 25°C (2), VIN = 5V, Io= 10mA unless otherwise noted.
Parameter Symbol Test Conditions Min Typ Max Unit
Quiescent Current IQ0°C TJ125°C 10 14 mA
Fixed Voltage Version
RMS Output Noise N 10HZf 10 kHZ0.003 %VO
Ripple Rejection Ratio RR f = 120 HZ, CO= 25µF60 72 dB
Cadj = 25µF
Thermal Regulation RTH TA= 25°C, 30ms Pulse 0.02 0.05 %/W
Long Term Stability TA= 125°C, 1000 Hrs 0.3 %VO
Notes:
(1) All parameters, except nominal output voltage are specified for the variable voltage version, allowing a wider Vin Range.
The specified limits also apply for the fixed voltage versions over the allowable input voltage range: GS1085-1.8 (3.2V - 7.0V), GS1085-2.5 (3.9V - 7.0V),
GS1085-3.3 (4.75V - 7.0V).
(2) To maintain the specified junction temperatures, low duty cycle pulse testing is required for most parameters.
Notes:
VREF = VOUT – VADJ = 1.25V (typ.)
VOUT = VREF x (1+R2/R1) + IADJ x R2
IADJ = 55µA(typ.)
(1) C1 needed if device is far away from filter capacitors
(2) C2 required for stability
Typical Application Circuit
VIN
5V
VOUT
3.3V
C1
10µF
C2
10µF
ADJ VREF
1
32
R1
125
1%
R2
205
1%
GS1085
Adjustable Voltage Regulator
++
VIN
5V VOUT
C1
10µF
C2
10µF
1
32
GS1085-1.8
GS1085-2.5
GS1085-3.3
Fixed Voltage Regulator
++
Document Number 74821 www.vishay.com
07-Mar-05 3
GS1085
Vishay Siliconix
--0.10
0.10
--0.05
0.05
0
--0.15
--0.20 20 40 60 80 100 120
Fig. 2 – Load Regulation
vs. Temperature
Output Voltage Deviation (%)
Temperature (°C)
0
20
40
60
80
100
--50 --25 0 25 50 75 100 125
Fig. 4 – Adjust Pin Current
Adjust Pin Current (µA)
Temperature (°C)
0
--1.0
--0.75
--0.5
--0.25
0.25
0.5
0.0
0.75
1.0
--20 0 20 40 60 80 100 120 140
Fig. 5 – Temperature Stability
Output Voltage Deviation (%)
Temperature (°C)
Iout = 0.5A
IOUT = 3A
0.5 1.0 2 2.5 3.01.5
Minimum Differential Voltage (V)
Output Current (A)
1.20
1.18
1.16
1.14
1.12
1.10
1.08
1.06
1.22
0
100 1K 100K10K 1M
Fig. 6 – Ripple Rejection
(with Cadj 25µF)
Ripple Rejection (dB)
Frequency (Hz)
20
30
40
50
60
70
80
10
12 4563
Fig. 3 – Minimum Load Current
(Adjustable Version)
Minimum Operating Current (mA)
Input / Output Differential Voltage (V)
2
4
6
8
10
0
TJ = 0°C
TJ = 25°C
TJ = 125°C
Fig. 1 – Dropout Voltage
vs. Output Current
COUT = 25µF
COUT = 25µF
COUT = 10µF
COUT = 10µF
Ratings and
Characteristic Curves (TA= 25°C unless otherwise noted)
GS1085
Vishay Siliconix
www.vishay.com Document Number 74821
407-Mar-05
Ratings and
Characteristic Curves (TA= 25°C unless otherwise noted)
--0.1
2.5A
0.1A
--0.05
0
0.05
0.1
40 80 120 160 200
Fig. 7 – Load Transient Response
Load Current
Output Voltage
(V, AC)
Time (µs)
0
VIN = 5V
CIN = 1µF
COUT = 10µF (Tantalum)
VOUT = 3.3V --100
7.0
6.0
--50
0
50
10 20 30 40 50
Fig. 8 – Line Transient Response
Input Voltage (V)
Output Voltage
(mV, AC)
Time (µs)
0
COUT = 10µF (Tantalum)
VOUT = 3.3V
Document Number 74821 www.vishay.com
07-Mar-05 5
GS1085
Vishay Siliconix
PART NUMBER OUTPUT VOLTAGE PACKAGE PACKING AMBIENT TEMP
(V) RANGE
GS1085CE/27F-E3 Adjustable
GS1085CE-18/27F-E3 1.8 TO-252AB Tape/Reel
GS1085CE-25/27F-E3 2.5 2500/Reel
GS1085CE-33/27F-E3 3.3
GS1085CM/31F-E3 Adjustable
GS1085CM-18/31F-E3 1.8 TO-263AB Tape/Reel - 20°C to + 85°C
GS1085CM-25/31F-E3 2.5 800/Reel
GS1085CM-33/31F-E3 3.3
GS1085CT/45F-E3 Adjustable
GS1085CT-18/45F-E3 1.8 TO-220AB Tube
GS1085CT-25/45F-E3 2.5 50/Tube
GS1085CT-33/45F-E3 3.3
Ordering Information
* E3 designates Lead (Pb)-free product
GS1085
Vishay Siliconix
www.vishay.com Document Number 74821
607-Mar-05
9.65
10.29
8.63
9.66
14.60
15.88
123
4.06
4.83
1.14
1.40
0.7 (max.)
2.28
2.80
0.50
1.00
1.14
1.40
2.54 (TYP.)
1.40 (max.)
TO-263
TO-252 (DPAK)
5.59
5.33 10.42
9.40
5.46
5.21
6.73
6.35
0.58
0.46
2.38
2.19
2.28 (TYP.)
0.88
0.64
13
2
1.27
1.02
0.51 (min.)
Dimensions in millimeters
10.66
9.66
6.35 Max.
3.42
2.54
4.08
3.54
6.85
5.85
16.51
14.23
14.73
12.70
1.77
1.15
1.01
0.38
2.79
2.29
(with plating)
4.82
3.56 1.39
0.51
1.14
0.31 2.92
2.04
(with plating)
TO-220
Case Outlines