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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.
Very Low Dropout 3.0 Amp Regulator With Enable
Features
u 350mV dropout @ 3A u Adjustable output from 1.2V to 4.8V u 2.5V and 1.8V options (5 pin parts also adjustable u u u u u u u u u u u u
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
SC1566
Applications
Battery powered systems Motherboards and notebook computers Peripheral cards Network cards Set top boxes Medical equipment
Typical Application Circuits(1)(2)
U1 SC1566I5T-2.5 VIN ENABLE 1 2 VIN EN VO ADJ 5 4
VO = See equation below
GND 3
R1
VO =
C2 R2
C1
1.200 (R1+ R2) Volts R2
U1 SC1566I5T-2.5 VIN ENABLE C1 1 2 VIN EN VO ADJ 5 4 C2 VO = 2.5V
GND 3
U1 SC1566IT-1.8 VIN 1 VIN VO 3 VO = 1.8V
GND 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 1, January 2001
1
SC1566
POWER MANAGEMENT Absolute Maximum Ratings
Parameter Input Voltage Power D i ssi pati on Thermal Resi stance Juncti on to Ambi ent SC 1566IM (TO-263) SC 1566IT (TO-220) Thermal Resi stance Juncti on to C ase SC 1566IM (TO-263) SC 1566IT (TO-220) Operati ng Ambi ent Temperature Range Operati ng Juncti on Temperature Range Storage Temperature Range Lead Temperature (Solderi ng) 10 Sec. ESD Rati ng (Human Body Model) Sy mbol VIN PD q JA Max 5.5 Internally Li mi ted 60 50 3 3 -40 to +85 -40 to +150 -65 to +150 300 2 U nits V W C /W
q JC 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 Qui escent C urrent
Sy mbol
Test C onditions
Min
Ty p
Max
U nits
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 Fi xed Voltage) Li ne Regulati on(1) Load Regulati on(1) D ropout 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
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V
% % mV
mV
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 (C ont.) D ropout Voltage(1)(2)
Sy mbol
Test C onditions
Min
Ty p
Max
U nits
IO = 1.5A
200
300 400
mV
IO = 3A
350
450 600
mV
Mi ni mum Load C urrent(3) C urrent Li mi t AD J 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 Pi n C urrent(4) Adjust Pi n Threshold(5) EN Enable Pi n C urrent Enable Pi n Threshold
IADJ VTH(ADJ)
VADJ = VREF 0.10
10 0.20
50 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
Ov er Temperature Protection Hi gh Tri p level Hysteresi s 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
SC 1566 5-PIN Versions Pin 1 2 Function VIN EN GND AD J VO
Ordering Information
D ev ice(1) SC 1566IM-X.X.TR SC 1566I5M-X.X.TR(2) SC 1566IT-X.X SC 1566I5T-X.X(2) P ackag e TO-263-3(3) TO-263-5(3) TO-220-3(4) TO-220-5(4)
TO-263-5
3 4 5
TAB IS GND
TO-220-5
SC 1566 3-PIN Versions Pin 1 2 Function VIN GND VO
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. (6) Only available in tube packaging. A tube contains 50 devices.
Block Diagram
TO-263-3
3
TAB IS GND
Note: (1) 3-pin versions are fixed output voltage only.
TO-220-3
* 5 lead versions only
Pin Descriptions
Pin N ame Pin D esciption 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 resi stors are used, the output voltage wi ll be (See Appli cati on C i rcui ts on page 1):
VO = 1.200 (R1 + R2) R2 Volts
EN GND VIN VO
Enable Input. Pulli ng thi s pi n below 0.4V turns the regulator off, reduci ng the qui escent current to a fracti on of i ts operati ng value. The devi ce wi ll be enabled i f thi s pi n i s left open. C onnect to VIN i f not bei ng used. Reference ground. Use the tab (electri cally connected to GND ) for heatsi nki ng. Input voltage. For regulati on at full load, the i nput to thi s pi n must be between (VO + 0.7V) and 5.5V. Mi ni mum VIN = 2.2V. Thi s pi n i s the power output of the devi ce.
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SC1566
POWER MANAGEMENT Typical Characteristics
Dropout Voltage vs. Output Current vs. Junction Temperature
500 150C 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 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 500
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
Output Voltage (2.5V) vs. Junction Temperature vs. Output Current
VIN = 5.5V
IO = 10mA
IO = 3A 2.480 2.470 2.460 2.450 -50 -25 0 25 50 TJ (C) 75 100 125 150
Reference Voltage vs. Junction Temperature vs. Output Current
1.225 VIN = 2.2V 1.220 1.215 1.210 VREF (V) IO = 10mA
Reference Voltage vs. Junction Temperature vs. Output Current
1.225 VIN = 5.5V 1.220 1.215 1.210 VREF (V) 1.205 1.200 1.195 1.190 1.185 1.180 1.175 IO = 10mA IO = 3A
1.205 1.200 1.195 1.190 1.185 1.180 1.175 -50
IO = 3A
-25
0
25
50 TJ (C)
75
100
125
150
-50
-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 VIN = 3.3V 690 680 670 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 IQ(OFF) (A) 10 8 6 4 2 12 VIN = 5.5V
Off-State Quiescent Current vs. Junction Temperature
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 22F, 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.
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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 120kW). 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. Using this figure, and assuming TA(MAX) = 85C, we can calculate the maximum thermal impedance allowable to maintain TJ 150C (see page 7):
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SC1566
POWER MANAGEMENT Applications Information (Cont.)
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.
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
Contact Information
Semtech Corporation Power Management Products Division 652 Mitchell Rd., Newbury Park, CA 91320 Phone: (805)498-2111 FAX (805)498-3804
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