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Final Electrical Specifications
LT3433 High Voltage Step-Up/Step-Down DC/DC Converter
September 2003
FEATURES
s s s s s s s s s s s s s s
DESCRIPTION
The LT(R)3433 is a 200kHz fixed-frequency current mode switching regulator that provides both step-up and stepdown regulation using a single inductor. The IC operates over a 4V to 60V input voltage range making it suitable for use in various wide input voltage range applications such as automotive electronics that must withstand both load dump and cold crank conditions. Internal control circuitry monitors system conditions and converts from single switch buck operation to dual switch bridged operation when required, seamlessly changing between step-down and step-up voltage conversion. Optional Burst Mode(R) operation reduces no-load quiescent current to 100A and maintains high efficiencies with light loads. Current limit foldback and frequency foldback help prevent inductor current runaway during start-up. Programmable soft-start helps prevent output overshoot at start-up. The LT3433 is available in a 16-lead thermally enhanced TSSOP package.
Automatic Step-Up and Step-Down Conversion Uses a Single Inductor Wide 4V to 60V Input Voltage Range VOUT from 3.3V to 20V Dual Internal 500mA Switches 100A No-Load Quiescent Current Low Current Shutdown 1% Output Voltage Accuracy 200kHz Operating Frequency Boosted Supply Pin to Saturate High Side Switch Frequency Foldback Protection Current Limit Foldback Protection Current Limit Unaffected by Duty Cycle 16-lead Thermally Enhanced TSSOP Package
APPLICATIO S
s s s
12V Automotive Systems Wall Adapter Powered Systems Battery Power Voltage Buffering
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
L1 100H CoEv DU1352-101M
4V to 60V to 5V DC/DC Converter with Burst Mode Operation
B160A VOUT 5V 4V VIN 8.5V: 125mA 8.5V VIN 60V: 350mA
Maximum Output Current vs VIN
500 VOUT = 5V MAXIMUM OUTPUT CURRENT (mA) BUCK 400
1N4148 VBST VIN 4V TO 60V 0.1F SW_H VIN 1nF100pF 68k VFB 100k 0.5% 305k 0.5% SGND 0.01F SS BURST_EN VC PWRGND VOUT LT3433 SW_L
B120A
47F
+
2.2F
300
EFFICIENCY (%)
1N4148 VBIAS 0.1F SHDN
200 BRIDGED 100
0
0
10
20
3433 TA01
30 VIN (V)
40
50
60
3433 TA01c
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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Efficiency
90 80 VIN = 13.8V 70 60 50 40 30 20 0.1 VIN = 4V
10 100 1 OUTPUT CURRENT (mA)
1000
3433 TA01b
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LT3433
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW SGND VBST SW_H VIN BURST_EN VC VFB SGND 1 2 3 4 5 6 7 8 17 16 SGND 15 SW_L 14 PWRGND 13 VOUT 12 VBIAS 11 SHDN 10 SS 9 SGND
Input Supply (VIN) .................................... -0.3V to 60V Boosted Supply (VBST) .............. -0.3V to VSW_H + 30V (VBST(MAX) = 80V) Internal Supply (VBIAS) ............................. - 0.3V to 30V SW_H Switch Voltage .................................. - 2V to 60V SW_L Switch Voltage ............................... - 0.3V to 30V Feedback Voltage (VFB) ............................... - 0.3V to 5V Operating Junction Temperature Range (Note 5) LT3433E (Note 6) ............................ - 40C to 125C LT3433I ........................................... - 40C to 125C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER LT3433EFE LT3433IFE
FE PART MARKING 3433EFE 3433IFE
FE PACKAGE 16-LEAD PLASTIC TSSOP
TJMAX = 125C, JA = 40C/W, JC = 10C/W EXPOSED PAD (PIN 17) MUST BE SOLDERED TO SGND
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The q denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 13.8V, VFB = 1.25V, VOUT = 5V, VBURST_EN = 0V, VBST - VIN = 5V, unless otherwise noted.
SYMBOL VIN VIN(UVLO) VOUT VBST IVIN PARAMETER Operating Voltage Range Undervoltage Lockout Undervoltage Lockout Hysteresis Operating Voltage Range Operating Voltage Range Normal Operation Burst Mode Operation Shutdown Internal Supply Output Voltage Operating Voltage Range IVBIAS Normal Operation Burst Mode Operation Shutdown Short-Circuit Current Limit Boost Supply Switch On-Resistance Output Supply Switch On-Resistance Shutdown Pin Thresholds Boost Supply Switch Drive Current Output Supply Switch Drive Current Switch Current Limit Foldback Current Limit ISS VFB Soft-Start Output Current Feedback Reference Voltage
q q
CONDITIONS
q
MIN 4
q
TYP 3.4 160
MAX 60 3.95 20 75 20
UNITS V V mV V V V A A A V V A A A mA V V mA/A mA/A A A A V V
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Enable Threshold
3.3 3.3 580 100 10 2.6 660 0.1 0.1 4.5 0.8 0.6 0.4
VBST < VSW_H + 20V VBST - VSW_H (Notes 2, 3) VVC < 0.6V VSHDN < 0.4V
q q q q q q q q
940 190 25 2.9 20 990
VBIAS
VVC < 0.6V VSHDN < 0.4V ISW = 500mA ISW = 500mA Disable Enable High Side Switch On, ISW = 500mA Low Side Switch On, ISW = 500mA VFB = 0V
q q q q q q q q
RSWH(ON) RSWL(ON) VSHDN IVBST/ISW IVOUT/ISW ILIM
1.2 1 1
30 30 0.5 3 1.224 1.215 0.7 0.35 5 1.231
50 50 0.9 9 1.238 1.245
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LT3433
ELECTRICAL CHARACTERISTICS
The q denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 13.8V, VFB = 1.25V, VOUT = 5V, VBURST_EN = 0V, VBST - VIN = 5V, unless otherwise noted.
SYMBOL VFB IFB gm AV ISW/VVC fO PARAMETER Feedback Reference Line Regulation VFB Pin Input Bias Current Error Amplifier Transconductance Error Amplifier Voltage Gain Control Voltage to Switch Transconductance Operating Frequency Foldback Frequency tON(MIN) tOFF(MIN) Minimum Switch On Time Minimum Switch Off Time VFB > 1V
q
CONDITIONS 5.5V VIN 60V
q q q
MIN
TYP 0.002 35
MAX 0.01 100 330
UNITS %/V nA umhos dB A/V
200
270 66 0.55
185 170
200 50
215 230 450 800
kHz kHz kHz ns ns
VFB = 0V RL = 35 (Note 4) RL = 35 (Note 4)
q q
250 500
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Supply current specification does not include switch drive currents. Actual supply currents will be higher. Note 3: "Normal Operation" supply current specification does not include IBIAS currents. Powering the VBIAS pin externally reduces ICC supply current. Note 4: Minimum times are tested using the high side switch with a 35 load to ground.
Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may impair device reliability. Note 6: The LT3433E is guaranteed to meet performance specifications from 0C to 125C junction temperature. Specifications over the - 40C to 125C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3433I is guaranteed over the full -40C to 125C operating junction temperature range.
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum Output Current vs VIN
500 VOUT = 5V MAXIMUM OUTPUT CURRENT (mA) BUCK
2.8
VBIAS OUTPUT VOLTAGE (V)
400
IVIN (A)
300
200 BRIDGED 100 SEE TYPICAL APPLICATION ON THE FIRST PAGE OF THIS DATA SHEET 0 10 20 30 VIN (V) 40 50 60
3433 G11
0
UW
VBIAS Output Voltage vs Temperature
620
VIN Supply Current vs VIN Supply Voltage
TA = 25C 590
2.6
560
2.4
530
2.2 -50
500
0 50 TEMPERATURE (C) 100 125
0
15
30 VIN (V)
45
60
3433 G02
3433 G01
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LT3433 TYPICAL PERFOR A CE CHARACTERISTICS
Soft-Start Current vs Temperature
7.0 6.5 6.0 1.232
SWITCH CURRENT LIMIT (mA)
ERROR AMP REFERENCE (V)
ISS (A)
5.5 5.0 4.5 4.0 -50
0 50 TEMPERATURE (C)
Oscillator Frequency vs Temperature
210
OSCILLATOR FREQUENCY (kHz)
205
OSCILLATOR FREQUENCY (kHz)
200
CURRENT LIMIT (mA)
195
190 -50
0 50 TEMPERATURE (C)
Maximum Boost Supply Switch Drive Current vs Boost Supply Voltage
70 70
65
IVOUT/ISW (mA/A) IBST/ISW (mA/A)
60
55
50
45 4 5 6 9 10 VBST - VSW_H (V) 7 8 11 12
4
UW
100
3433 G03
Error Amp Reference vs Temperature
700
Switch Current Limit vs VFB
TA = 25C
1.231
600
1.230
500
1.229
400
125
1.228 -50
300 0 50 TEMPERATURE (C) 100 125
0
0.2
0.6 0.4 VFB (V)
0.8
1.0
3433 G05
3433 G04
Oscillator Frequency vs VFB
200 TA = 25C 150
725 750
Switch Current Limit vs Temperature
100
700
50
675
100
125
0
0
0.2
3433 G06
0.6 0.4 VFB (V)
0.8
1.0
3433 G07
650 -50
0 50 TEMPERATURE (C)
100
125
3433 G08
Maximum Output Supply Switch Drive Current vs Output Supply Voltage
65
60
55
50
45 4 5 6 7 8 VOUT (V)
3433 G09 3433 G10
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LT3433
PI FU CTIO S
SGND (Pins 1, 8, 9, 16): Low Noise Ground Reference. VBST (Pin 2): Boosted Switch Supply. This "boosted" supply rail is referenced to the SW_H pin. Supply voltage is maintained by a bootstrap capacitor tied from the VBST pin to the SW_H pin. A 1F capacitor is generally adequate for most applications. The charge on the bootstrap capacitor is refreshed through a diode, typically connected from the converter output (VOUT), during the switch-off period. Minimum off-time operation assures that the boost capacitor is refreshed each switch cycle. The LT3433 supports operational VBST supply voltages up to 75V (absolute maximum) as referenced to ground. SW_H (Pin 3): Boosted Switch Output. This is the current return for the boosted switch and corresponds to the emitter of the switch transistor. The boosted switch shorts the SW_H pin to the VIN supply when enabled. The drive circuitry for this switch is boosted above the VIN supply through the VBST pin, allowing saturation of the switch for maximum efficiency. The "ON" resistance of the boosted switch is 0.8. VIN (Pin 4): Input Power Supply. This pin supplies power to the boosted switch and corresponds to the collector of the switch transistor.This pin also supplies power to most of the IC's internal circuitry if the VBIAS pin is not driven externally. This supply will be subject to high switching transient currents so this pin requires a high quality bypass capacitor that meets whatever application-specific input ripple current requirements exist. See Applications Information. BURST_EN (Pin 5): Burst Mode Enable Pin. Shorting this pin to SGND enables Burst Mode operation. If Burst Mode operation is not desired, connecting this pin to VBIAS or VOUT will disable the burst function. VC (Pin 6): Error Amplifier Output. The voltage on the VC pin corresponds to the maximum switch current per oscillator cycle. The error amplifier is typically configured as an integrator circuit by connecting an RC network from this pin to ground. This circuit typically creates the dominant pole for the converter regulation feedback loop. Specific integrator characteristics can be configured to optimize transient response. See Applications Information. VFB (Pin 7): Error Amplifier Inverting Input. The noninverting input of the error amplifier is connected to an internal 1.231V reference. The VFB pin is connected to a resistor divider from the converter output. Values for the resistor connected from VOUT to VFB (RFB1) and the resistor connected from VFB to ground (RFB2) can be calculated to program converter output voltage (VOUT) via the following relation: VOUT = 1.231 * (RFB1 + RFB2)/RFB2 The VFB pin input bias current is 35nA, so use of extremely high value feedback resistors could cause a converter output that is slightly higher than expected. Bias current error at the output can be estimated as: VOUT(BIAS) = 35nA * RFB1 The voltage on VFB also controls the LT3433 oscillator frequency through a "frequency-foldback" function. When the VFB pin voltage is below 0.8V, the oscillator runs slower than the 200kHz typical operating frequency. The oscillator frequency slows with reduced voltage on the pin, down to 50kHz when VFB = 0V. The VFB pin voltage also controls switch current limit through a "current-limit foldback" function. At VFB = 0V, the maximum switch current is reduced to half of the normal value. The current limit value increases linearly until VFB reaches 0.6V when the normal maximum switch current level is restored. The frequency and current-limit foldback functions add robustness to short-circuit protection and help prevent inductor current runaway during start-up. SS (Pin 10): Soft Start. Connect a capacitor (CSS) from this pin to ground. The output voltage of the LT3433 error amplifier corresponds to the peak current sense amplifier output detected before resetting the switch output(s). The soft-start circuit forces the error amplifier output to a zero peak current for start-up. A 5A current is forced from the SS pin onto an external capacitor. As the SS pin voltage ramps up, so does the LT3433 internally sensed peak current limit. This forces the converter output current to ramp from zero until normal output regulation is achieved. This function reduces output overshoot on converter start-up.
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LT3433
PI FU CTIO S
The time from VSS = 0V to maximum available current can be calculated given a capacitor CSS as: tSS = (2.7 * 105)CSS or 0.27s/F SHDN (Pin 11): Shutdown. If the SHDN pin is externally pulled below 0.5V, low current shutdown mode is initiated. During shutdown mode, all internal functions are disabled, and ICC is reduced to 10A. This pin is intended to receive a digital input, however, there is a small amount of input hysteresis built into the SHDN circuit to help assure glitchfree mode switching. If shutdown is not desired, connect the SHDN pin to VIN. VBIAS (Pin 12): Internal Local Supply. Much of the LT3433 circuitry is powered from this supply, which is internally regulated to 2.5V through an on-board linear regulator. Current drive for this regulator is sourced from the VIN pin. The VBIAS supply is short-circuit protected to 5mA. The VBIAS supply only sources current, so forcing this pin above the regulated voltage allows the use of external power for much of the LT3433 circuitry. When using external drive, this pin should be driven above 3V to assure the internal supply is completely disabled. This pin is typically diodeconnected to the converter output to maximize conversion efficiency. This pin must be bypassed with at least a 0.1F ceramic capacitor to SGND. VOUT (Pin 13): Converter Output Pin. This pin voltage is compared with the voltage on VIN internally to control operation in single or 2-switch mode. When the ratios of the two voltages are such that a >75% duty cycle is required for regulation, the low side switch is enabled. Drive bias for the low side switch is also derived directly from this pin. PWRGND (Pin 14): High Current Ground Reference. This is the current return for the low side switch and corresponds to the emitter of the low side switch transistor. SW_L (Pin 15): Ground Referenced Switch Output. This pin is the collector of the low side switch transistor. The low side switch shorts the SW_L pin to PWRGND when enabled. The series impedance of the ground-referenced switch is 0.6.
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LT3433
BLOCK DIAGRA W
VBIAS 12 1.25V BURST CONTROL CIRCUITS BIAS BURST_EN 5 VIN 4 SENSE AMPLIFIER VBST COMPARATOR BOOSTED DRIVER SW_H 3 2 SLOPE COMP OSCILLATOR 200kHz FREQUENCY CONTROL MODE CONTROL SWITCH CONTROL LOGIC SW_L DRIVER GND 14 15 VFB 30% LOAD ERROR AMPLIFIER 1.231V VC SHDN 6 11 7
+
Burst Mode CONTROL 15% LOAD 5A SHUTDOWN
-
0.7V SS 10 VOUT SGND 1, 8, 9,16 13
3433 BD
VOUT
+
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LT3433
APPLICATIO S I FOR ATIO
Overview
The LT3433 is a high input voltage range, step-up/stepdown DC/DC converter IC using a 200kHz constant frequency, current mode architecture. Dual internal switches allow the full input voltage to be imposed across the switched inductor, such that both step-up and step-down modes of operation can be realized using the same single inductor topology. The LT3433 has provisions for high efficiency, low load operation for battery-powered applications. Burst Mode operation reduces average quiescent current to 100A in no load conditions. A low current shutdown mode can also be activated, reducing total quiescent current to 10A. Much of the LT3433's internal circuitry is biased from an internal low voltage linear regulator. The output of this regulator is brought out to the VBIAS pin, allowing bypassing of the internal regulator. The associated internal circuitry can be powered directly from the output of the converter, increasing overall converter efficiency. Using externally derived power also eliminates the IC's power dissipation associated with the internal VIN to VBIAS regulator. Theory of Operation (See Block Diagram) The LT3433 senses converter output voltage via the VFB pin. The difference between the voltage on this pin and an internal 1.231V reference is amplified to generate an error voltage on the VC pin which is, in turn, used as a threshold for the current sense comparator. During normal operation, the LT3433 internal oscillator runs at 200kHz. At the beginning of each oscillator cycle, the switch drive is enabled. The switch drive stays enabled until the sensed switch current exceeds the VC-derived threshold for the current sense comparator and, in turn, disables the switch driver. If the current comparator threshold is not obtained for the entire oscillator cycle, the switch driver is disabled at the end of the cycle for 250ns. This minimum off-time mode of operation assures regeneration of the VBST bootstrapped supply. If the converter input and output voltages are close together, proper operation in normal buck configuration would require high duty cycles. The LT3433 senses this
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condition as requiring a duty cycle greater than 75%. If such a condition exists, a second switch is enabled during the switch on time, which acts to pull the output side of the inductor to ground. This "bridged" operation allows voltage conversion to continue when VOUT approaches or exceeds VIN. Shutdown The LT3433 incorporates a low current shutdown mode where all IC functions are disabled and the VIN current is reduced to 10A. Pulling the SHDN pin down to 0.4V or less activates shutdown mode. Burst Mode Operation The LT3433 employs low current Burst Mode functionality to maximize efficiency during no load and low load conditions. Burst Mode function is disabled by shorting the BURST_EN pin to either VBIAS or VOUT. Burst Mode function is enabled by shorting BURST_EN to SGND. When the required switch current, sensed via the VC pin voltage, is below 30% of maximum, the Burst Mode function is employed. When the voltage on VC drops below the 30% load level, that level of sense current is latched into the IC. If the output load requires less than this latched current level, the converter will overdrive the output slightly during each switch cycle. This overdrive condition forces the voltage on the VC pin to continue to drop. When the voltage on VC drops below the 15% load level, switching is disabled, and the LT3433 shuts down most of its internal circuitry, reducing quiescent current to 100A. When the voltage on the VC pin climbs back to 20% load level, the IC returns to normal operation and switching resumes. Antislope Compensation Most current mode switching controllers use slope compensation to prevent current mode instability. The LT3433 is no exception. A slope compensation circuit imposes an artificial ramp on the sensed current to increase the rising slope as duty cycle increases. Unfortunately, this additional ramp corrupts the sensed current value, reducing the achievable current limit value by the same amount as the added ramp represents. As such, current limit is typically reduced as duty cycles increase.
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LT3433
APPLICATIO S I FOR ATIO
The LT3433 contains circuitry to eliminate the current limit reduction associated with slope-compensation, or antislope compensation. As the slope compensation ramp is added to the sensed current, a similar ramp is added to the current limit threshold reference. The end result is that current limit is not compromised so the LT3433 can provide full power regardless of required duty cycle. Mode Switching The LT3433 senses operational duty cycle by directly monitoring VIN and VOUT. Voltage drops associated with pass and catch diodes are estimated internally such that mode switching occurs when the duty cycle required for continuous buck operation is greater than 75%. If such a condition exists, a second switch is enabled during the switch on time, changing operation to a dual switch bridged configuration. Because the voltage available across the switched inductor is greater in bridged mode, duty cycle will decrease. The output current in bridged mode is not continuous, so switch currents are considerably higher than while operating in buck mode. In order to maximize available output power, continuous operation and low ripple currents are recommended. Switch currents will increase by a factor of 1/(1 - DC) during bridged mode, so this mode of operation is typically the gating item for converter drive capability. IOUT(MAX) = ISW(MAX) * (1 - DC) = [0.5A - (IL / 2)] * (1 - DC) where IL is the ripple current in the inductor. It is also important to note that IOUT cannot be considered equivalent to ILOAD during bridged operation. Most of the converter's switch drive power is derived from the generated output supply, so IOUT must also accommodate this current requirement. During single-switch buck operational conditions, switch drive current is negligible in terms of output current; however, during bridged operation, these currents can become significant. These output derived switch drive currents will increase the current loading on VIN by the same 1/(1 - DC) factor as the switch currents. As maximum switch current is referenced to that coming from the VIN supply, the available maximum
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switch current will be reduced by this required drive current. IDRIVE = DC * 2 * ISW(MAX) * ISWDRIVE(MAX) Using 50mA/A for the required drive current for each switch yields the portion of switch current used to drive the switches is: ISW(DRIVE) = DC * 2 * ISW(MAX) * 0.05/(1 - DC) Removing drive currents from the available maximum switch current yields: ISW(MAX)' = ISW(MAX) * [1 - DC * 2 * ISW(MAX) * 0.05/(1 - DC)] where ISW(MAX)' is maximum switch current available to the load during bridged operation. The maximum load current can then be calculated as: ILOAD(MAX) = ISW(MAX)' * (1 - DC) which reduces to: ILOAD(MAX) = [0.5A - (IL/2)] * (1 - 1.1 * DC) Design Equations
VIN SW_H LT3433 SW_L L VOUT
3433 AI01
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Constants: VSWH = voltage drop across boosted switch VSWL = voltage drop across grounded switch VF = forward drop of external Schottky diodes f0 = operating frequency Duty Cycle (continuous operation): DCBUCK = (VOUT + 2VF)/(VIN - VSWH + VF) DCBRIDGED = (VOUT + 2VF)/(VOUT + VIN + 2VF - VSWH - VSWL)
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LT3433
APPLICATIO S I FOR ATIO
Ripple current:
IL(P -P) =
(VOUT + 2VF ) * (1- DC )
L * fO
Inductor Selection The primary criterion for inductor value selection in LT3433 applications is the ripple current created in that inductor. Design considerations for ripple current are the amount of output ripple and the ability of the internal slope compensation waveform to prevent current mode instability. The LT3433 maximizes available dynamic range using a slope compensation generator that generates a continuously increasing slope as duty cycle increases. The slope compensation waveform is calibrated at 80% duty cycle to compensate for ripple currents up to 12.5% of IMAX, or ~ 60mA. Ripple current can be calculated as:
IL(P -P) =
(VOUT + 2VF ) * (1- DC )
L * fO
This relation can be used to determine minimum inductance sizes for various values of VOUT using the DC = 80% calibration: LMIN = (VOUT + 1.5V) * (1 - 0.8) 60mA * 200kHz)
VOUT 4V 5V 9V 12V LMIN 92H 108H 175H 225H
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Discontinuous operation occurs when the ripple current in the inductor is greater than twice the load current (ILOAD) in buck mode, or greater than ILOAD/(1 - DC) during bridged mode. Current mode instability is not a concern during discontinuous operation so inductor values smaller than LMIN can be used. If such a small inductor is used, however, it must be assured that the converter never enters continuous operation at duty cycles greater than 50% to prevent current mode instability. Design Example VIN(MIN) = 4V, VOUT = 5V, L = 150H Using VF = 0.75V yields: DC = (VOUT + 2VF)/(VOUT + VIN + 2VF - VSWH - VSWL) = (5V + 1.5V)/(4V + 5V + 1.5V - 0.6V - 0.5V) = 0.69 IL = (VOUT + 2VF) * (1 - DC) * (L * f0)-1 = (5V + 1.5V) * (1 - 0.69) * (150H * 200kHz)-1 = 67mA ILOAD(MAX) = ISW(MAX) * (1 - 1.1 * DC) = [0.5A - (1/2 * 0.07)](1 - 1.1 * 0.69) = 0.112A
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LT3433
TYPICAL APPLICATIO
DS1 B160A
D1 1N4148 C1 0.1F VIN 4V TO 60V VBST SW_L
+
C7 2.2F
C6 100pF
R2 510k 5%
PACKAGE DESCRIPTIO
6.60 0.10 4.50 0.10 SEE NOTE 4
RECOMMENDED SOLDER PAD LAYOUT 4.30 - 4.50* (.169 - .177) 0 - 8
0.09 - 0.20 (.0036 - .0079)
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE
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Burst Only Low Noise 5V Maintenance Supply
L1 33H DS2 B160A SW_H PWRGND LT3433 VIN VOUT BURST_EN VC VFB R1 2.2M 5% SGND VBIAS SHDN SS IN LT1761-5 SHDN GND C3 10F
3433 TA03
D2 1N4148 C2 0.1F VOUT 5V 10mA
OUT BYP
C4 0.01F
C5 2.2F
FE Package 16-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1663)
Exposed Pad Variation BB
3.58 (.141) 4.90 - 5.10* (.193 - .201) 3.58 (.141) 16 1514 13 12 1110 9
2.94 (.116) 0.45 0.05 1.05 0.10 0.65 BSC 12345678 1.10 (.0433) MAX 2.94 6.40 (.116) BSC
0.45 - 0.75 (.018 - .030)
0.65 (.0256) BSC
0.195 - 0.30 (.0077 - .0118)
0.05 - 0.15 (.002 - .006)
FE16 (BB) TSSOP 0203
4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE
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LT3433
TYPICAL APPLICATIO
VIN 4V TO 60V
+
C7 2.2F
C5 1nF C4 100pF R1 68k R2 100k 0.5% R3 305k 0.5%
RELATED PARTS
PART NUMBER LT1076/LT1076HV LT1676 LT1765 LT1766/LT1956 LT1767 LT1776 LT1976 LT3010 LTC3412/LTC3414 LTC3414 DESCRIPTION 1.6A (IOUT), 100kHz High Efficiency Step-Down DC/DC Converters 60V, 440mA (IOUT), 100kHz High Efficiency Step-Down DC/DC Converter 25V, 2.75A (IOUT), 1.25MHz High Efficiency Step-Down DC/DC Converter 60V, 1.2A (IOUT), 200kHz/500kHz High Efficiency Step-Down DC/DC Converters 25V, 1.2A (IOUT), 1.25MHz High Efficiency Step-Down DC/DC Converter 40V, 550mA (IOUT), 200kHz High Efficiency Step-Down DC/DC Converter 60V, 1.2A (IOUT), 200kHz High Efficiency Micropower (IQ < 100A) Step-Down DC/DC Converter 80V, 50mA Low Noise Linear Regulator 2.5A (IOUT), 4MHz Synchronous Step-Down DC/DC Converters 4A (IOUT), 4MHz Synchronous Step-Down DC/DC Converter COMMENTS VIN: 7.3V to 45V/64V, VOUT(MIN): 2.21V, IQ: 8.5mA, ISD: 10A, DD5/DD7, TO220-5/TO220-7 VIN: 7.4V to 60V, VOUT(MIN): 1.24V, IQ: 3.2mA, ISD: 2.5A, SO-8 VIN: 3V to 25V, VOUT(MIN): 1.20V, IQ: 1mA, ISD: 15A, SO-8, TSSOP16E VIN: 5.5V to 60V, VOUT(MIN): 1.20V, IQ: 2.5mA, ISD: 25A, TSSOP16/TSSOP16E VIN: 3V to 25V, VOUT(MIN): 1.20V, IQ: 1mA, ISD: 6A, MS8/MS8E VIN: 7.4V to 40V, VOUT(MIN): 1.24V, IQ: 3.2mA, ISD: 30A, N8, SO-8 VIN: 3.3V to 60V, VOUT(MIN): 1.20V, IQ: 100A, ISD: <1A, TSSOP16E VIN: 1.5V to 80V, VOUT(MIN): 1.28V, IQ: 30A, ISD: <1A, MS8E VIN: 2.5V to 5.5V, VOUT(MIN): 0.8V, IQ: 60A, ISD: <1A, TSSOP16E VIN: 2.3V to 5.5V, VOUT(MIN): 0.8V, IQ: 64A, ISD: <1A, TSSOP20E VIN: 4V to 36V, VOUT(MIN): 0.8V, IQ: 670A, ISD: 20A, QFN32, SSOP28 VIN: 5.5V to 60V, VOUT(MIN): 1.20V, IQ: 2.5mA, ISD: 30A, TSSOP16E VIN: 2.5V to 5.5V, VOUT(MIN): 2.5V, IQ: 25A, ISD: <1A, MS10
3433ia LT/TP 0903 1K REV A * PRINTED IN USA
LTC3727/LTC3727-1 36V, 500kHz High Efficiency Step-Down DC/DC Controllers LT3430/LT3431 LTC3440 60V, 2.75A (IOUT), 200kHz/500kHz High Efficiency Step-Down DC/DC Converters 600mA (IOUT), 2MHz Synchronous Buck-Boost DC/DC Converter with 95% Efficiency
12 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
U
4V-60V to 5V at 100mA DC/DC Converter Burst Disabled
DS1 B160A L1 100H DS2 B160A C6 47F VBST SW_L D2 1N4148 C1 0.1F VOUT 5V 100mA SW_H PWRGND LT3433 VOUT VIN BURST_EN VC VFB SGND VBIAS SHDN SS C3 0.01F D1 1N4148 C2 0.1F
3433 TA02
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2003

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