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Very Low Dropout 3.0 Amp Regulator With Enable
POWER MANAGEMENT Description
The SC1566 is a high performance positive voltage regulator designed for use in applications requiring very low dropout voltage at up to 3 Amps. Since it has superior dropout characteristics compared to regular LDOs, it can be used to supply 2.5V on motherboards or 2.8V on peripheral cards from the 3.3V supply thus allowing heat sink size reduction or elimination. Additionally, the five pin versions of SC1566 have an enable pin, to further reduce power dissipation while shut down. The SC1566 provides excellent regulation over variations in line, load and temperature. The SC1566 is available as three terminal fixed output voltage and five terminal fixed or adjustable output voltage devices with enable. Two package options are available: TO-263 and TO-220.
SC1566
Features
350mV dropout @ 3A Adjustable output from 1.2V to 4.8V 2.5V and 1.8V options (5 pin parts also adjustable externally using resistors) Over current and over temperature protection Enable pin 10A quiescent current in shutdown Low reverse leakage (output to input) Full industrial temperature range TO-220 and TO-263 packages
Applications
Battery powered systems Motherboards and notebook computers Peripheral cards Network cards Set top boxes Medical equipment
Typical Application Circuits(1)(2)
VIN ENABLE 1 2 U1 SC1566I5T-2.5 VIN EN GND 3 C1 VO ADJ 5 4
VO = See equation below
R1
VO =
C2 R2
1.200 (R1+ R2) Volts R2
VIN ENABLE C1
1 2
U1 SC1566I5T-2.5 VIN EN GND 3 VO ADJ
5 4 C2
VO = 2.5V
VIN
1
U1 SC1566IT-1.8 VIN GND VO
3
VO = 1.8V
C1
2
C2
Notes: (1) Maximum VO setpoint for 1.8V parts = 5.4V (2) This device is designed to operate with ceramic input and output capacitors
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Revision: April 27, 2005
1
SC1566
POWER MANAGEMENT Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied.
Parameter Input Voltage Power Dissipation Thermal Resistance Junction to Ambient TO-263-X TO-220-X Thermal Resistance Junction to Case TO-263-X TO-220-X Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) 10 Sec. ESD Rating (Human Body Model)
Symbol VIN PD J A
Max 7 Internally Limited 60 50 3 3 -40 to +85 -40 to +150 -65 to +150 300 2
Units V W C/W
J C TA TJ TSTG TLEAD V ESD
C/W C C C C kV
Electrical Characteristics
Unless specified: VEN = VIN. Adjustable Option (VADJ > VTH(ADJ)): VIN = 2.2V to 5.5V and IO = 10A to 3A. Fixed Options (VADJ = GND): VIN = (VO + 0.7V) to 5.5V and IO = 0A to 3A. Values in bold apply over the full operating temperature range.
Parameter VIN Supply Voltage Range Quiescent Current
Symbol
Test Conditions
Min
Typ
Max
Units
VIN IQ VIN = 3.3V VIN = 5.5V, VEN = 0V
2.2 0.75 10
5.5 1.75 35
V mA A
VO Output Voltage(1) (Internal Fixed Voltage) Line Regulation(1) Load Regulation(1) Dropout Voltage(1)(2) REG(LINE) REG(LOAD) VD VIN = (VO + 0.25V) to 5.5V, IOUT = 10mA VIN = VO + 0.7V IO = 10mA VO VIN = VO + 0.7V, IO = 10mA -1% -2% 0.035 0.2 1 VO +1% +2% 0.3 0.4 5 10 IO = 500mA 75 100 150 mV % % mV V
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SC1566
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: VEN = VIN. Adjustable Option (VADJ > VTH(ADJ)): VIN = 2.2V to 5.5V and IO = 10A to 3A. Fixed Options (VADJ = GND): VIN = (VO + 0.7V) to 5.5V and IO = 0A to 3A. Values in bold apply over the full operating temperature range.
Parameter VO (Cont.) Dropout Voltage(1)(2)
Symbol
Test Conditions
Min
Typ
Max
Units
IO = 1.5A
200
300 400
mV
IO = 3A
350
450 600
mV
Minimum Load Current(3) Current Limit ADJ Reference Voltage(1)
IO ICL
VIN = VO + 0.7V 3.0
1 4.5
10 6.5
A A
VREF
VIN = 2.2V, VADJ = VOUT, IO = 10mA
1.188 1.176
1.200
1.212 1.224
V
Adjust Pin Current(4) Adjust Pin Threshold(5) EN Enable Pin Current Enable Pin Threshold
IADJ VTH(ADJ)
VADJ = VREF 0.10
10 0.20
200 0.40
nA V
IEN VIH VIL
VEN = 0V, VIN = 3.3V VIN = 3.3V VIN = 3.3V 1.8
1.5
10
A V
0.4
Over Temperature Protection High Trip level Hysteresis THI THYST 175 10 C C
Notes: (1) Low duty cycle pulse testing with Kelvin connections required. (2) Defined as the input to output differential at which the output voltage drops to 1% below the value measured at a differential of 0.7V. (3) Required to maintain regulation. Voltage set resistors R1 and R2 are usually utilized to meet this requirement. Adjustable versions only. (4) Guaranteed by design. (5) When VADJ exceeds this threshold, the "Sense Select" switch disconnects the internal feedback chain from the error amplifier and connects VADJ instead.
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SC1566
POWER MANAGEMENT Pin Configurations
SC1566 5-PIN Versions Pin 1 2 Function VIN EN GND AD J VO
Ordering Information
Device(1) SC1566IM-X.X.TR SC1566IM-X.XTRT(6) SC1566I5M-X.X.TR(2) SC1566I5MX.XTRT(2)(6) SC1566IT-X.X SC1566IT-X.XT(6) SC1566I5T-X.X(2)(5) SC1566I5TX.XT(2)(5)(6) P ackag e TO-263-3(3)
TO-263-5(3)
TO-263-5
3 4 5
TO-220-3(4)
TO-220-5(4)
TAB IS GND
TO-220-5
SC1566 3-PIN Versions Pin 1 2 Function VIN GND VO
SC1566I5T-X.XSB(2)(5) SC1566I5TX.XSBT(2)(5)(6)
TO-220-5(4)
TO-263-3
3
TAB IS GND
Note: (1) 3-pin versions are fixed output voltage only.
Notes: (1) Where -X.X denotes voltage options. Available voltages are: 2.5V and 1.8V. (2) Output voltage can be adjusted using external resistors, see Pin Descriptions below. (3) Only available in tape and reel packaging. A reel contains 800 devices. (4) Only available in tube packaging. A tube contains 50 devices. (5) T-XX = Straight in-line; T-XX-SB = Single Bend. (6) Lead free product. This product is fully WEEE and RoHS compliant. TO-220-3
Pin Descriptions
Pin Name Pin Desciption AD J Thi s pi n, when grounded, sets the output voltage to that set by the i nternal feedback resi stors. If external feedback resistors are used, the output voltage will be (See Application Circuits on page 1):
VO = 1.200 (R1 + R2) R2 Volts
EN GND VIN VO
Enable Input. Pulling this pin below 0.4V turns the regulator off, reducing the quiescent current to a fraction of its operating value. The device will be enabled if this pin is left open. Connect to VIN if not being used. Reference ground. Use the tab (electrically connected to GND) for heatsinking. Input voltage. For regulation at full load, the input to this pin must be between (VO + 0.7V) and 5.5V. Minimum VIN = 2.2V. This pin is the power output of the device.
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SC1566
POWER MANAGEMENT Block Diagram
* 5 lead versions only
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SC1566
POWER MANAGEMENT Typical Characteristics
Dropout Voltage vs. Output Current vs. Junction Temperature
500 450 400 350 VD (mV) 300 250 200 150 100 50 0 0.0 0.5 1.0 1.5 IO (A) 2.0 2.5 3.0 3.5 25C VD (mV) 0C -40C 150C 500 450 400 350 300 250 200 150 100 50 0 -50 -25 0 25 50 TJ (C) 75 100 125 150 IO = 0.5A IO = 1.5A IO = 3A
Dropout Voltage vs. Junction Temperature vs. Output Current
Output Voltage (2.5V) vs. Junction Temperature vs. Output Current
2.550 2.540 2.530 2.520 VO (V) VO (V) 2.510 2.500 2.490 2.480 2.470 2.460 2.450 -50 -25 0 25 50 TJ (C) 75 100 125 150 IO = 3A IO = 10mA VIN = 3.2V 2.550 2.540 2.530 2.520 2.510 2.500 2.490 2.480 2.470 2.460 2.450 -50
Output Voltage (2.5V) vs. Junction Temperature vs. Output Current
VIN = 5.5V
IO = 10mA
IO = 3A
-25
0
25
50 TJ (C)
75
100
125
150
Reference Voltage vs. Junction Temperature vs. Output Current
1.225 1.220 1.215 1.210 VREF (V) VREF (V) 1.205 1.200 1.195 1.190 1.185 1.180 1.175 -50 -25 0 25 50 TJ (C) 75 100 125 150 IO = 3A IO = 10mA VIN = 2.2V 1.225 1.220 1.215 1.210 1.205 1.200 1.195 1.190 1.185 1.180 1.175 -50
Reference Voltage vs. Junction Temperature vs. Output Current
VIN = 5.5V
IO = 3A
IO = 10mA
-25
0
25
50 TJ (C)
75
100
125
150
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SC1566
POWER MANAGEMENT Typical Characteristics (Cont.)
Quiescent Current vs. Junction Temperature
700 690 680 670 IQ(OFF) (A) IQ (A) 660 650 640 630 620 610 600 -50 -25 0 25 50 TJ (C) 75 100 125 150 0 -50 -25 0 25 50 TJ (C) 75 100 125 150 VIN = 3.3V 12 10 8 6 4 2
Off-State Quiescent Current vs. Junction Temperature
VIN = 5.5V
Applications Information
Introduction The SC1566 is intended for applications such as graphics cards where high current capability and very low dropout voltage are required. It provides a very simple, low cost solution that uses very little pcb real estate and typically does not require a heatsink. Additional features include an enable pin to allow for a very low power consumption standby mode, and a fully adjustable output (5-pin versions). Component Selection Input capacitor: a 4.7F or 10F ceramic capacitor is recommended. This allows for the device being some distance from any bulk capacitance on the rail. Additionally, input droop due to load transients is reduced, improving load transient response. Additional capacitance may be added if required by the application. Output capacitor: a minimum bulk capacitance of 2.2F, along with a 0.1F ceramic decoupling capacitor is recommended. Increasing the bulk capacitance will improve the overall transient response. The use of multiple lower value ceramic capacitors in parallel to achieve the desired bulk capacitance will not cause stability issues. Although designed for use with ceramic output capacitors, the SC1566 is extremely tolerant of output capacitor ESR values and thus will also work comfortably with tantalum output capacitors. For reference, the phase-margin contour of Figure 1. can be used
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to choose an appropriate output capacitor for a given stability requirement. Noise immunity: in very electrically noisy environments, it is recommended that 0.1F ceramic capacitors be placed from IN to GND and OUT to GND as close to the device pins as possible. External voltage selection resistors (5-pin parts): the use of 1% resistors, and designing for a current flow 10A is recommended to ensure a well regulated output (thus R2 120k). Thermal Considerations The power dissipation in the SC1566 is approximately equal to the product of the output current and the input to output voltage differential:
PD (VIN - VOUT ) * I O
The absolute worst-case dissipation is given by:
PD ( MAX ) = (VIN ( MAX ) - VOUT
( MIN )
)* I
O ( MAX )
+ VIN ( MAX ) * I Q ( MAX )
For a typical scenario, VIN = 3.3V 5%, VOUT = 2.8V and IO = 2.5A, therefore: VIN(MAX) = 3.465V, VOUT(MIN) = 2.744V and IQ(MAX) = 1.75mA, Thus PD(MAX) = 1.81W.
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SC1566
POWER MANAGEMENT Applications Information (Cont.)
Using this figure, and assuming TA(MAX) = 85C, we can calculate the maximum thermal impedance allowable to maintain TJ 150C (see page 7):
R TH ( J - A )( MAX ) =
(T
J( MAX )
- TA (MAX ) )
PD (MAX )
=
(150 - 85 ) = 36 C / W
1.81
R TH ( J - C )( MAX ) = 3 C / W and R TH ( C - S ) = 0 C / W , therefore R TH ( S - A )( MAX ) = 33 C / W
This should be achievable for the TO-263 package using pcb copper area to aid in conducting the heat away from the device, such as a large (~2 squ. inch) pad connected to the tab of the device. Internal ground/power planes and air flow will also assist in removing heat. For higher power dissipations it may be necessary to use a small heatsink and the TO-220 package.
Co=2.2uF, Stable Region: Unstable Region:
Co=22uF, Stable Region: Unstable Region:
3mA
3mA
30mA
30mA
Load
300mA 300mA
Load
0.001
0.01
0.1
1
3A 10
0.001
0.01
0.1
1
3A 10
ESR(Ohms)
ESR(Ohms)
Co=220uF, Stable Region: Unstable Region:
3mA
30mA
Load
300mA
0.001
0.01
0.1
1
3A 10
ESR(Ohms)
Figure 1. Phase-margin Contour Plot
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SC1566
POWER MANAGEMENT Outline Drawing - T0-263-3
Minimum Land Pattern - TO-263-3
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SC1566
POWER MANAGEMENT Outline Drawing - TO-263-5
Minimum Land Pattern - TO-263-5
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SC1566
POWER MANAGEMENT Outline Drawing - TO-220-3
Outline Drawing - TO-220-5
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SC1566
POWER MANAGEMENT Outline Drawing - TO-220-5 (T-XX-SB Option)
Contact Information
Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804
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