LT1302 LINER
Document overview
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Technical content
Figure 1. 2-Cell to 5V/600mA DC/DC Converter mode operation at heavy load. further reduced to 15µA in shutdown. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation.
2 CELLS
A UGWA WU WARBSOLUTEX I T I S WU UPACKAGE/ORDER I FOR ATIO V Consult factory for Industrial and Military grade parts. ORDER PART NUMBER LT1302CN8 LT1302CS8 LT1302CN8-5 LT1302CS8-5 S8 PART MARKING 1302 13025 SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS IQ Quiescent Current V SHDN = 0.5V, VFB = 1.3V l 200 300 µA VSHDN = 1.8V l 15 25 µA VIN Input Voltage Range 2.0 V l 2.2 8 V VFB Feedback Voltage (LT1302) V C = 0.4V l 1.22 1.24 1.26 V Feedback Pin Bias Current (LT1302) V FB = 1V 100 nA Output Sense Voltage (LT1302-5) V C = 0.4V l 4.85 5.05 5.25 V Output Ripple Voltage (LT1302-5) V C = 0.4V 50 mV Sense Pin Resistance to Ground (LT1302-5) 420 k Ω VOS Offset Voltage See Block Diagram 15 mV Comparator Hysteresis (Note 1) 5 mV Oscillator Frequency Current Limit Not Asserted (Note 2) 175 220 265 kHz l 160 310 kHZ DC Maximum Duty Cycle 75 86 95 % tON Switch On Time Current Limit Not Asserted 3.9 µs tOFF Switch Off Time 0.7 µs Output Line Regulation 2 < V IN < 8V l 0.06 0.15 %/V VCESAT Switch Saturation Voltage I SW = 2A 310 400 mV l 475 mV Switch Leakage Current V SW = 5V, Switch Off l 0.1 10 µA Switch Current Limit V C = 0.4V (Burst Mode Operation) 1 A VC = 1.25V (Full Power) (Note 3) l 2.0 2.8 3.9 A Error Amplifier Voltage Gain 0.9V ≤ VC ≤ 1.2V, ΔVC/ΔVFB 50 75 V/ V VSHDNH Shutdown Pin High l 1.8 V VSHDNL Shutdown Pin Low l 0.5 V ISHDN Shutdown Pin Bias Current V SHDN = 5V l 82 0 µA VSHDN = 2V 3 µA VSHDN = 0V l 0.1 1 µA IT Pin Resistance to Ground 3.9 k Ω TA = 25°C, VIN = 2.5V, unless otherwise noted.ELECTRICAL C CHARA TERISTICSCD The l denotes specifications which apply over the 0°C to 70°C temperature range. Note 1: Hysteresis is specified at DC. Output ripple depends on capacitor size and ESR. Note 2: The LT1302 operates in a variable frequency mode. Switching frequency depends on load inductance and operating conditions and may be above specified limits. Note 3: Minimum switch current 100% tested. Maximum switch current guaranteed by design. TOP VIEW GND VC SHDN (SENSE*)FB PGND SW V IN IT N8 PACKAGE 8-LEAD PDIP S8 PACKAGE 8-LEAD PLASTIC SO *FIXED VERSION PINS 1 AND 8 ARE INTERNALLY CONNECTED IN SOIC PACKAGE TJMAX = 125°C, θJA = 100°C/W (N8) TJMAX = 125°C, θJA = 80°C/W (S8)
TYPICAL PERFORMANCE CHARACTERISTICS UW TEMPERATURE (°C) –50 SATURATION VOLTAGE (mV) 400 350 300 250 200 150 100 –25 02 5 5 0
1302 G03
ISW = 2A TEMPERATURE (°C) –50 FEEDBACK VOLTAGE (V) 1.250 1.245 1.240 1.235 1.230 1.225 1.220 1.215 1.210 1.205 1.200 –25 02 5 5 0
1302 G04
SUPPLY VOLTAGE (V) QUIESCENT CURRENT (µA) 500 450 400 350 300 250 200 150 100
1302 G01
TA = 25°C No-Load Quiescent Current Circuit of Figure 1 TEMPERATURE (°C) –50 SENSE RESISTANCE (kΩ ) 600 500 400 300 200 100 –25 02 5 5 0
1302 G05
TEMPERATURE (°C) –50 QUIESCENT CURRENT (µA) 300 250 200 150 100 –25 02 5 5 0
1302 G06
VIN = 2.5V SWITCH OFF TEMPERATURE (°C) –50 OFFSET VOLTAGE (mV) –25 02 5 5 0
1302 G07
TEMPERATURE (°C) –50 OUTPUT VOLTAGE (V) 5.100 5.075 5.050 5.025 5.000 4.975 4.950 4.925 4.900 –25 02 5 5 0
1302 G08
TEMPERATURE (°C) –50 ON-TIME (µs) 5.0 4.5 4.0 3.5 3.0 2.5 2.0 –25 02 5 5 0
1302 G09
SWITCH CURRENT (A) VCESAT (V) 600 500 400 300 200 100 12 34
1302 G02
TA = 25°C Switch Saturation Voltage Switch Saturation Voltage LT1302 Feedback Voltage LT1302-5 Sense Pin Resistance Quiescent Current Error Amplifier Offset Voltage LT1302-5 Output Voltage Maximum On-Time
TYPICAL PERFORMANCE CHARACTERISTICS UW TEMPERATURE (°C) –50 DUTY CYCLE (%) 100 –25 02 5 5 0
1302 G10
TEMPERATURE (°C) –50 FREQUENCY (kHz) 300 275 250 225 200 175 150 –25 02 5 5 0
1302 G11
SHUTDOWN VOLTAGE (V) SHUTDOWN CURRENT (µA) 4 5
1302 G12
TA = 25°C GND (Pin 1): Signal Ground. Feedback resistor and 0.1µF ceramic bypass capacitor from VIN should be connected directly to this pin. VC (Pin 2): Frequency Compensation Pin. Connect series RC to GND. Keep trace short. SHDN (Pin 3): Shutdown. Pull high to effect shutdown; tie to ground for normal operation. FB/Sense (Pin 4): Feedback/Sense. On the LT1302 this pin connects to CMP1 input. On the LT1302-5 this pin connects to the output resistor string. PI FU CTIO S U UU IT (Pin 5): Normally left floating. Addition of a 3.3k resistor to GND forces the LT1302 into current mode at light loads. Efficiency drops at light load but increases at medium loads. See Applications Information section. V IN (Pin 6): Supply Pin. Must be bypassed with: (1) a 0.1µF ceramic to GND, and (2) a large value electrolytic to PGND. When V IN is greater than 5V, a low value resistor (2Ω to 10Ω ) is recommended to isolate the V IN pin from input supply noise. Maximum Duty Cycle Oscillator Frequency Shutdown Pin Bias Current LT1302-5 Output Voltage vs Load Current LOAD CURRENT (A) OUTPUT VOLTAGE (V) 5.20 5.15 5.10 5.05 5.00 4.95 4.90 4.85 4.80 0.1 0.2 0.3 0.4
1302 G13
VIN = 2.2V VIN = 3V VIN = 4V Maximum Output Power* Boost Mode INPUT VOLTAGE (V) OUTPUT POWER (W)
1302 G14
- APPROXIMATE 6 10
SW (Pin 7): Switch Pin. Connect inductor and diode here. Keep layout short and direct. Figure 2. LT1302 Block Diagram
1302 F02
heavy loads, control is passed to error amplifier A1. 36mV below VIN for A2 to trip and turn off the oscillator.
1302 F03
Figure 3. LT1302-5 Block Diagram
closed-loop system, frequency compensation is required. Mode, dropping to 4.97V in current mode. case since peak currents will necessarily be higher. Table 1. Recommended Inductors VENDOR PART NO. VALUE( µH) PHONE NO.
- The ripple voltage is now over 500mV
Figure 4. Low ESR Output Capacitor Results in Stable Figure 5. Inexpensive Electrolytic Capacitor Has High network for VIN is recommended as detailed in Figure 6. Figure 6. A 10Ω /1µF Decoupling Network at VIN Is
1302 F06
Table 2 lists capacitor vendors along with device types. Table 2. Recommended Capacitors VENDOR SERIES TYPE PHONE NO. in switching regulator applications.
voltage rises above its threshold. of damping is observed, and behavior is more controlled. slight underdamping is still noticeable. undershoot less than 100mV and settles in less than 1ms. exceed 1/10 of the compensation capacitor value. circuit. Figure 7 shows the setup. is connected with no resistor. Figure 7b details response. Figure 7b. 0.1µF from VC to Ground. Figure 7. Boost Converter with Simulated Load
1302 F07
Figure 7c. 0.01µF from VC to Ground. output voltage and inductor current without the resistor. Figure 7d. 0.1µF with 10k Series RC.
1302 F08
Figure 8. Addition of R1 Eliminates Low Frequency
dV/dt signals away from the pin. tors R1 and R2 should be close to the feedback pin (pin4). Noise can easily be coupled into this pin if care is not taken.
1302 F08c
Figure 9. Suggested Component Placement for LT1302 at frequencies out of the audio band.
1302 F09
Table 3. S8 Package, 8-Lead Plastic SO separate ground trace up under the package as shown. the heat generated by the device. Table 3 lists thermal resistance for the SO package. well as board size and shape.
APPLICATIONS INFORMATIONWU UU As an example, consider a boost converter with the following specifications: VIN = 3V VOUT = 6V IOUT = 700mA Total power loss in the LT1302, assuming R = 0.15Ω and VD = 0.45V, is: Using the CS8 package with 100 sq. mm topside and backside heat sinking: ΔT = (312mW)(84°C/W) = 25.9°C rise With the N8 package: ΔT = 31.2°C At a 70°C ambient, die temperature would be 101.2°C. Pm A mW mW mW D = () ( ) − ×× − + − ×× () +−() =+ = 700 0 15 60 4 5 3 07 6 01 5 60 4 5 3 07 6 01 5 0 7 6 0 45 3 223 89 312 . . Ω
Single Cell to 5V/150mA Converter
1302 TA03
1.5V CELL 100k 100k 0.01µF 20k 100pF 0.1µFC2 220µF 47µF L1 = COILCRAFT DO3316-332 D1 = MOTOROLA MBRS130LT3 C1 = AVX TPSD476M016R0150 C2 = AVX TPSE227M010R0100 COILCRAFT (708) 639-2361 100k 56.2k 4.99k 36.5k 301k (169k FOR 3.3V) 10Ω 5V/150mA OUTPUT 3.3µH 220Ω + + LT1302 FB GNDPGND SHDNVIN SW IT VC SW1 AO SW2GND VINIL SET FB LT1073 2N3906 2V to 12V/120mA Converter VIN IT NC VC SW 0.1µF LT1302 PGND SHDN SHUTDOWN FB GND RC 20k 100k 866k C C 0.02µF 100µF D1 +C2 33µF 33µF 3.3µH LT1302 • TA04 C1 = AVX TPSD107M010R0100 C2 = AVX TPSD336M025R0200 OUTPUT 12V 120mA 100pF D1 = MOTOROLA MBRS130LT3 L1 = COILCRAFT DO3316-332
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 represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. TYPICAL APPLICATIONSU 2 Li-Ion Cell to 5.8V/600mA DC/DC Converter 3 Cell to 3.3V Buck-Boost Converter with Auxiliary 12V Regulated Output
1302 TA05
1% 200pF 100k 24k 4700pF 10Ω 0.1µF T1C T1A T1D T1E VIN 2.5V-8V 47µF 16V T1B 22µF 25V 100µF 16V 13V 330µF 6.3V 3.3V OUTPUT 400mA 330k 3.3µF 150k 12V 120mA T1 = D1, D2 = C1 = C2 = C3 = DALE LPE-6562-A069, 1:3:1:1:1 TURNS RATIO, 10µH PRIMARY. DALE (605) 665-9301 MOTOROLA MBRS130LT3 AVX TPSE107016R0100 AVX TPSE337006R0100 AVX TPSD476016R0150 LT1121 GND IN SHDN ADJ OUT VIN IT FB SHDN SHUTDOWN 22µH 22µH VC PGND 1µF 10Ω LT1302 GND SW 20k
1302 TA07
5.8V 600mA VIN 4V TO 9V 100k MBRS130LT3 365k ++ C1 100µF 16V 220µF 10V 220µF 10V 10nF DUTY CYCLE = VOUT VIN + VOUT PEAK SWITCH VOLTAGE = VIN + VOUT L1, L2 = COILCRAFT DO3316-223 C1 = AVX TPSE107016R0100 C2, C3 = AVX TPSE227010R0100
Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 l FAX: (408) 434-0507 l TELEX: 499-3977 LINEAR TECHNOLOGY CORPORA TION 1995 LT/GP 0295 10K • PRINTED IN USA PACKAGE DESCRIPTIONU Dimensions in inches (millimeters) unless otherwise noted. N8 0694 0.045 – 0.015 (1.143 – 0.381) 0.100 – 0.010 (2.540 – 0.254) 0.065 (1.651) TYP 0.045 – 0.065 (1.143 – 1.651) 0.130 – 0.005 (3.302 – 0.127) 0.015 (0.380) MIN 0.018 – 0.003 (0.457 – 0.076) 0.125 (3.175) MIN 12 3 4 87 6 5 0.255 – 0.015* (6.477 – 0.381) 0.400* (10.160) MAX 0.009 – 0.015 (0.229 – 0.381) 0.300 – 0.325 (7.620 – 8.255) 0.325 +0.025 –0.015 +0.635 –0.3818.255() *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm). 1 2 3 4 0.150 – 0.157* (3.810 – 3.988) 8 7 6 5 0.189 – 0.197* (4.801 – 5.004) 0.228 – 0.244 (5.791 – 6.197) 0.016 – 0.050 0.406 – 1.270 0.010 – 0.020 0°– 8° TYP 0.008 – 0.010 (0.203 – 0.254) SO8 0294 0.053 – 0.069 (1.346 – 1.752) 0.014 – 0.019 (0.355 – 0.483) 0.004 – 0.010 (0.101 – 0.254) 0.050 (1.270) BSC *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 8-Lead Plastic DIP 8-Lead Plastic SOIC