Simple Boost Controller SC2603 versatile, low-cost, voltage-mode

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Simple Boost Controller SC2603 versatile, low-cost, voltage-mode

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SC2603
Simple Boost Controller
SC2603 versatile, low-cost, voltage-mode controller designed input DC/DC power supply applications. simple, fixed-voltage boost regulator implemented using SC2603 with minimum external components. small device footprint allows compact circuit design. SC2603 features include temperature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, internally compensated error amplifier. Pulse pulse current limiting implemented sensing differential voltage across external resistor, appropriately sized board trace. SC2603 operates fixed frequency 200kHz, providing optimum compromise between efficiency, external component size, cost.
Features
cost small size Switch mode efficiency reference voltage accuracy Over-current protection 800mA output drive input power source need external compensation network SOT23-6 fully WEEE RoHS compliant
Applications
Portable Devices Flat Panel Auxiliary Supplies Peripheral Card Supplies Industrial Power Supplies High Density DC/DC Conversion
Typical Application Circuit
optional Enable (open collector) Open Drain with pull down impedance Gate SC2603 VOUT
EN/SS
Revision: April 2006
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SC2603
POWER MANAGEMENT Absolute Maximum Ratings
Exceeding specifications below result permanent damage device, device malfunction. Operation outside parameters specified Electrical Characteristics section implied.
Parameter Input Voltage Storage Temperature Range Maximum Junction Temperature Lead Temperature (Soldering) Sec. Thermal Resistance, Junction Ambient(1) Thermal Resistance, Junction Case Electrical Surge Discharge(2)
Symbol TSTG TLEAD
Maximum -0.3 +150
Units °C/W °C/W
Note: Mounting larger than square inch sided printed circuit board with minimum ounce copper Human model.
Electrical Characteristics
VIN= 12V; 25V; -40°C 125°C unless otherwise specified.
Parameter Reference Feedback urrent escent urrent Load Regulati Regulati urrent Threshold Osci llator Frequency Osci llator Frequency ycle UVLO Threshold UVLO Hysteresi Source urrent urrent Soft Start harge urrent Internal Ramp Peak Internal Ramp Valley Enable Threshold
Symbols VREF
onditions
1.225
1.250
1.275
nits
VEN/SS, urrent VO=25V 0.1A VIN=5V VO=25V 100mA 25OC VREF/2
VUVLO
rampi
ISOURCE ISINK VR_PEAK VR_VALLEY VTH_EN
12V, GATE 10nF 12V, GATE 10nF
Pull down below level sable output
0.09
0.12
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Configuration
View
EN/SS GATE
Ordering Information
umbers 2603S (1)(2) 2603E ackag OT23-6
SOT23-6
Note: Only available tape reel packaging. reel contains 3000 devices. Lead free product. This product fully WEEE RoHS compliant
Descriptions
Name EN/SS Gate Function Error amplifier input (-). Device ground. Enable/Soft Start Pin. Gate driver output. Device Input Voltage. Current Sense Input
Block Diagram
OSCILLATOR
Gate
Current Limit
EN/SS
1.25V 70mV
1.25V
UVLO
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Theory Operation
SC2603 versatile, low-cost, voltage-mode controller designed DC/DC power supply applications. normal condition, SC2603 operats fixed 200KHz. exception that when voltage drops half, frequency will shifted fouth 200KHz. SC2603 features include temperature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, internally compensated error amplifier. Pulse pulse current limiting implemented sensing differential voltage across external resistor, appropriately sized board trace.
Application Information
Soft-Start Soft-start prevents DC-DC converter from drawing excessive current from power source during start soft-start time made sufficiently long, then output will enter regulation without overshoot. external capacitor connected from EN/SS ground. After part's input voltage surpasses UVLO, EN/SS allowed charge capacitor with 60µA. When 100mV reached EN/SS pin, internal comp node 0.4V. SC2603 will start switching, converter output comes into regulation. Because voltage follows EN/SS voltage, finally, EN/SS voltage will clamped 1.25V same refernece voltage. Setting Output Voltage external resistive divider with center tied sets output voltage.
VOUT
SC2603
Under Voltage Lockout under voltage lockout circuit SC2603 assures that gate driver output remains state whenever supply voltage drops below parameters. Lockout occurs falls below 3.8V. Normal operation resumes once rises above 4.2V.
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Application Information
Over Current Protection over-current protection implemented sensing resistor internal current-limit comparator with threshold 70mV. switching current through sensing resistor causing voltage drop reachs 70mV, SC2603 will immediately turn gate pulse limit current through power switch. figure below shows over-current waveforms. input current begins increase load IOUT builds until hits threshold VOUT begins drop IOUT starts increasing toward while remain same. there events happening. VOUT half regulating voltage. this point, internal oscillator runs into frequency shift mode shifts frequency fourth operating frequency. diode starts conducting current without limit causing fall supply current limit. Finally, VOUT both drops zero becomes input supply current limit. filter necessary filter noise ensure accurate sensing. value sensing resistor caculated following equation:
PEAK
Where IPEAK input peak current through power MOSFET.
IOUT
VOUT
Over Current Waveforms
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Applications Information
Layout Guidelines Careful attention layout requirements necessary successful implementation SC2603 controller. High currents switching 200kHz present application their effect ground plane voltage differentials must understood minimized. high power parts circuit should laid first. ground plane should used, number position ground plane interruptions should such unnecessarily compromise ground plane integrity. Isolated semi-isolated areas ground plane deliberately introduced constrain ground currents particular areas, example input capacitor bottom Schottky ground. loop formed output Capacitor(s) (Cout), (Q1), current sensing resistor, Schottky (D1) must kept small possible. This loop contains high current, fast transition switching. Connections should wide short possible minimize loop inductance. Minimizing this loop area will reduce EMI, lower ground injection currents, resulting electrically "cleaner" grounds rest system minimize source ringing, resulting more reliable gate switching signals. connection between junction output capacitor should wide trace copper region. should short practical. Since this connection fast voltage transitions, keeping this connection short will minimize EMI. Output Capacitor(s) (Cout) should located close load possible, fast transient load currents supplied Cout only, connections between Cout load must short, wide copper areas minimize inductance resistance. SC2603 best placed over isolated ground plane area. soft-start capacitor, decoupling capacitor, current sensing filter capacitor should also connected this ground area. This isolated ground area should connected main ground trace that runs from ground side output capacitor. this possible, connected ground path between Output Capacitor Cin, loop. Under circumstances should returned ground inside Cin, loop. Input voltage SC2603 should supplied from power rail through 2.2~10 resistor, should decoupled directly 0.1µF~1µf ceramic capacitor, trace lengths should short possible. pass filter required filter leading edge current spikes current sensing resistor. filter capacitor needs very close reduce noise pickup.
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Applications Information (Cont.)
Layout diagram SC2603
Vout
12VIN
20uH
0.1uF 0.1uF SC2603 EN/SS Gate
Cout
Heavy lines indicate critical loop carrying high pulsating current. inductance this loop needs minimized.
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Applications Circuit
boost converter
470u 18uH VOUT=25V
330u/35V
Enable (open drain) 0.1u Gate SC2603 120p
AO4442
1.78K
EN/SS
Open Drain with pull down impedance
Bill Material
Item Quantity Reference Part 470u/Alum 330u/Alum 0.1u 120p 1N5819 18uH AO4442 1.78K SC2603 SOT23-6 SEMTECH COOPER Alpha Omega footprint Vendor SANYO SANYO
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Typical Characteristics
Error Amplifier: Gain Phase
Load Regulation (VIN 12V, 25V)
25.5
Gain 100.0E+0 10.0E+6 Phase
Phase (deg)
Gain (dB)
Output Voltage
24.5
23.5
Output Current
1.0E+3
10.0E+3
100.0E+3
1.0E+6
Frequency (Hz)
Efficiency (VIN 12V, 25V)
Line Regulation 25V,
26.000
25.500
Output Voltage
Efficiency
25.000
24.500
24.000
23.500
23.000
Output Current
Input oltage
(VIN 12V, 25V)
Frequency Shift (VFB FSW)
25.6
25.4
Output Voltage
25.2
24.8
24.6
24.4
24.2
Output Current
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Typical Characteristics
Reference Voltage Temperature UVLO Hysteresis Temperature
1.26
REFERENCE VOLTAGE
1.255 1.25 1.245 1.24 1.235 1.23 1.225
UVLO HYSTERESIS
VIN=12V
VIN=5V
1.22
TEMPERATURE (oC)
Oscillator Frequency Temperature
Current Limit Threshold Temperature
CURRENT LIMIT THRESHOLD (mV)
OSCILLATOR FREQUENCY (kHz)
TEMPERATURE (OC)
UVLO Threshold Temperature
UVLO THRESHOLD
2005 Semtech Corp.
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SC2603
POWER MANAGEMENT Outline Drawing SOT23-6
DIMENSIONS MILLIMETERS INCHES
1.45 0.90 0.00 0.15 1.15 1.30 0.25 0.50 0.08 0.22 2.80 2.90 3.00 1.50 1.60 1.75 2.80 0.95 1.90 0.30 0.45 0.60 (0.60) 0.10 0.20 0.20
TIPS
.035 .057 .000 .006 .035 .045 .051 .020 .010 .003 .009 .110 .114 .118 .060 .063 .069 .110 .037 .075 .012 .018 .024 (.024) .004 .008 .008
SEATING PLANE
GAGE PLANE
0.25
(L1)
DETAIL
DETAIL
SIDE VIEW
NOTES: CONTROLLING DIMENSIONS MILLIMETERS (ANGLES DEGREES).
DATUMS DETERMINED DATUM PLANE -H3. DIMENSIONS "E1" INCLUDE MOLD FLASH, PROTRUSIONS GATE BURRS.
Land Pattern SOT23-6
DIMENSIONS MILLIMETERS INCHES
(.098) .055 .037 .024 .043 .141 (2.50) 1.40 0.95 0.60 1.10 3.60
NOTES: THIS LAND PATTERN REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES MET.
Contact Information
Semtech Corporation Power Management Products Division Flynn Road, Camarillo, 93012 Phone: (805)498-2111 (805)498-3804
2005 Semtech Corp.
www.semtech.com

Simple Boost Controller SC2603 versatile, low-cost, voltage-mode

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