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POWER MANAGEMENT Description
The SC4211 is a high performance positive voltage regulator designed for use in applications requiring very low Input voltage and very low dropout voltage at up to 1 amp. It operates with a Vin as low as 1.4V, with output voltage programmable as low as 0.5V. The SC4211 features ultra low dropout, ideal for applications where Vout is very close to Vin. Additionally, the SC4211 has an enable pin to further reduce power dissipation while shutdown. The SC4211 provides excellent regulation over variations in line, load and temperature. The SC4211 is available in the SOIC-8EDP (Exposed Die Pad) package. The output voltage can be set via an external divider or to 0.5V depending on how the FB pin is configured.
Very Low Input /Very Low Dropout 1 Amp Regulator With Enable
Features
Input Voltage as low as 1.4V 250mV dropout @ 1A Adjustable output from 0.5V to 3.3V Over current and over temperature protection Enable pin 10A quiescent current in shutdown Low reverse leakage (output to input) Full industrial temperature range Available in SOIC-8EDP package
SC4211
Applications
Telecom/Networking cards Motherboards/Peripheral cards Industrial Applications Wireless infrastructure Set top boxes Medical equipment Notebook computers Battery powered systems
Typical Application Circuits
SC4211
4 NC VIN EN NC NC VO FB GND 5 6 7 8
VIN ENABLE
3 2 1
VO
R1
VO
C2
=
0.5 (R1 + R2) R2
Volts
C1
U1
R2
SC4211
4 NC VIN EN NC NC VO FB GND 5 6 7 8
VIN ENABLE
3 2 1
VO = 0.5V
C1
U1
C2
Revision October 18, 2004
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SC4211
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 Vin, EN, Vo, FB Absolute Voltage Power Dissipation Thermal Resistance Junction to Ambient SOIC-8EDP(1) Thermal Resistance Junction to Case SOIC-8EDP(1) Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering) 10 Sec. ESD Rating (Human Body Model)
Symbol
Max 7
Units V W C/W C/W C C C C kV
PD JA JC TA TJ TSTG TLEAD V ESD
Internally Limited 36 5.5 -40 to +85 -40 to +150 -65 to +150 300 2
Note: (1) 2 square inch of FR-4, double sided, 1 oz. minimum copper weight.
Electrical Characteristics
Unless specified: VEN = VIN, VFB = VO, VIN = 1.40V to 5.5V, VIN = (VO + 0.5V) to 5.5V and IO = 1mA to 1A. Values in bold apply over the full operating temperature range.
Parameter VIN Supply Voltage Range Qui escent C urrent
Symbol
Test C onditions
Min
Typ
Max
U nits
VIN IQ VIN = 3.3V, IOUT = 0A VIN = 5.5V, VEN = 0V
1.40
5.5 3 10 50
V mA A
VO Output Voltage(1) (Internal Fi xed Voltage) Li ne Regulati on(1) REG(LINE) VO VIN = VO + 0.5V, IOUT = 10mA Full IOUT , and VIN Range VIN = (VO + 0.5V), VIN < 3.3V, IOUT = 10mA VIN = (VO + 0.5V), VIN > 3.3V, IOUT = 10mA Load Regulati on(1) D ropout Voltage(1)(2) REG(LOAD) VD VIN = (VO + 0.5V), IOUT = 10mA to 1A IO = 10mA -1.5% -3% 0.25 0.5 0.5 2.5 VO +1.5% +3% 1.0 1.5 1.5 10 20 IO = 500mA 90 200 300 mV % % % mV V
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 1.5% below the value measured at a differential of 0.5V. (3) Required to maintain regulation. Voltage set resistors R1 and R2 are usually utilized to meet this requirement. (4) Guaranteed by design.
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SC4211
POWER MANAGEMENT Electrical Characteristics (Cont.)
Unless specified: VEN = VIN, VFB = VO, VIN = 1.40V to 5.5V, VIN = (VO + 0.5V) to 5.5V and IO = 1mA to 1A. 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 = 1A
200
400 500
mV
Minimum Load Current(3) Current Limit(4) F eed b ack Reference Voltage(1)
IO ICL
VIN = VO + 0.5V 1.1 1.5
1
mA A
VREF
VIN = 3.3V, VFB = VOUT, IO = 10mA Full IOUT , and VIN Range
0.495 0.485
0.5
0.505 0.515
V
Feedback Pin Current(4) EN Enable Pin Current Enable Pin Threshold
IADJ
VFB = VREF
80
200
nA
IEN VIH VIL
VEN = 0V, VIN = 3.3V VIN = 3.3V VIN = 3.3V 1.6
1.5
10
A V
0.4
Over Temperature Protection High Trip level Hysteresis THI THYST 160 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 1.5% below the value measured at a differential of 0.5V. (3) Required to maintain regulation. Voltage set resistors R1 and R2 are usually utilized to meet this requirement. (4) Guaranteed by design.
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SC4211
POWER MANAGEMENT Ordering Information
Part Number SC4211STRT
(1)(2)(3)
P ackag e SOIC-8EDP
Temp. Range (TA) -40 to +85 OC
SC4211EVB
Evaluation Board
Note: (1) Available voltage is : 0.5V or Output voltage can be adjusted using external resistors, see Pin Descriptions. (2) Only available in tape and reel packaging 2500 devices for the SOIC-8EDP package. (3) Lead free product.
Pin Configuration
Top View Bottom View
GND
NC EN VIN NC
SOIC-8EDP
GND FB VO NC
GND FB VO NC
8 7 6 5
Exposed Die Pad
1 2 3 4
NC EN VIN NC
SOIC-8EDP
Pin Descriptions
Pin Name Pin Description FB When this pin is connected to the Vo pin, the output voltage will be set at 0.5V If external feedback resistors are used, the output voltage will be (See Application Circuits on page 1):
VO = 0.5 (R1 + R2) R2 Volts
EN GND VIN
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. Note: The GND pin and the exposed die pad must be connected together at the IC pin. Use the exposed die pad on the device for heatsinking. Input voltage. For regulation at full load, the input to this pin must be between (VO+ 0.5V) and 5.5V. Minimum VIN = 1.4V. A large bulk capacitance should be placed closely to this pin to ensure that the input supply does not sag below 1.4V. Also a minimum of 4.7uF ceramic capacitor should be placed directly at this pin. The pin is the power output of the device. A minimum of 10uF ceramic capacitor should be placed directly at this pin.
VO
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SC4211
POWER MANAGEMENT Block Diagram
VIN Rsense VOUT
Vpump
++ Vdd
0.5V Ref EN UVLO FB
GND
Thermal Shutdown
Vout Vin
+ -
Reverse Voltage Shutdown
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SC4211
POWER MANAGEMENT Applications Information
Introduction The SC4211 is intended for applications 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. Additional features include an enable pin to allow for a very low power consumption standby mode, and a fully adjustable output. Component Selection Input capacitor: A large bulk capacitance of about 100uF should be closely placed to the input supply pin of the SC4211 to ensure that Vin does not sag below 1.4V. Also a minimum of 4.7F ceramic capacitor is recommended to be placed directly next to the Vin pin. 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 10F, 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 SC4211 is extremely tolerant of output capacitor ESR values and thus will also work comfortably with tantalum output capacitors. 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: 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 SC4211 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 = 1A, therefore: VIN(MAX) = 3.465V, VOUT(MIN) = 2.744V and IQ(MAX) = 1.75mA, Thus PD(MAX) = .722W. Using this figure, and assuming TA(MAX) = 70C, we can calculate the maximum thermal impedance allowable to maintain TJ 150C:
R TH(J-A)(MAX) =
(T
J(MAX)
- TA(MAX) )
PD(MAX)
=
(150 - 70) = 110C/W
.722
This should be achievable for the SOIC-8EDP package using PCB copper area to aid in conducting the heat away, such as one square inch of copper connected to the ground pins of the device. Internal ground/power planes and air flow will also assist in removing heat. For higher ambient temperatures it may be necessary to use additional copper area.
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SC4211
POWER MANAGEMENT Outline Drawing - SOIC-8EDP
Land Pattern - SOIC-8EDP
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SC4211
POWER MANAGEMENT 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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