LT1317/LT1317B Micropower, 600kHz PWM DC/DC Converters U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ 100µA Quiescent Current Operates with VIN as Low as 1.5V 600kHz Fixed Frequency Operation Starts into Full Load Low-Battery Detector Active in Shutdown Automatic Burst Mode Operation at Light Load (LT1317) Continuous Switching at Light Loads (LT1317B) Low VCESAT Switch: 300mV at 500mA Pin for Pin Compatible with the LT1307/LT1307B U APPLICATIONS ■ ■ ■ ■ ■ ■ ■ ■ The LT ®1317/LT1317B are micropower, fixed frequency step-up DC/DC converters that operate over a wide input voltage range of 1.5V to 12V. The LT1317 features automatic shifting to power saving Burst ModeTM operation at light loads. High efficiency is maintained over a broad 300µA to 200mA load range. Peak switch current during Burst Mode operation is kept below 250mA for most operating conditions which results in low output ripple voltage, even at high input voltages. The LT1317B does not shift into Burst Mode operation at light loads, eliminating low frequency output ripple at the expense of light load efficiency. The LT1317/LT1317B contain an internal low-battery detector with a 200mV reference that stays alive when the device goes into shutdown. Cellular Telephones Cordless Telephones Pagers GPS Receivers Battery Backup Portable Electronic Equipment Glucose Meters Diagnostic Medical Instrumentation No-load quiescent current of the LT1317 is 100µA and shuts down to 30µA. The internal NPN power switch handles a 500mA current with a voltage drop of just 300mV. The LT1317/LT1317B are available in MS8 and SO-8 packages. , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. U TYPICAL APPLICATION 2-Cell to 3.3V Converter Efficiency L1 10µH 90 2.2VIN C1 47µF VIN LBI SW FB LT1317 2 CELLS SHUTDOWN SHDN VC RC 33k CC 3.3nF LBO GND R1 1M 1% 80 3.3V 200mA + R2* 604k 1% D1: MBR0520 L1: SUMIDA CD43-100 * FOR 5V OUTPUT, R2 = 332k, 1% Figure 1. 2-Cell to 3.3V Boost Converter C2 47µF EFFICIENCY (%) + D1 3VIN 1.65VIN 70 60 50 1317 F01 40 0.3 1 10 100 LOAD CURRENT (mA) 1000 1317 TA01 1 LT1317/LT1317B W W W AXI U U ABSOLUTE RATI GS (Note 1) VIN, LBO Voltage ..................................................... 12V SW Voltage ............................................... – 0.4V to 30V FB Voltage .................................................... VIN + 0.3V VC Voltage ................................................................ 2V LBI Voltage ............................................ 0V ≤ VLBI ≤ 1V SHDN Voltage ............................................................ 6V Junction Temperature .......................................... 125°C Operating Temperature Range Commercial ........................................... 0°C to 70°C Industrial ............................................ – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................ 300°C U W U PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW VC FB SHDN GND 1 2 3 4 8 7 6 5 LBO LBI VIN SW LT1317CMS8 LT1317BCMS8 MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 160°C/W MS8 PART MARKING ORDER PART NUMBER TOP VIEW VC 1 8 LBO FB 2 7 LBI SHDN 3 6 VIN GND 4 5 SW LT1317CS8 LT1317BCS8 LT1317IS8 LT1317BIS8 S8 PACKAGE 8-LEAD PLASTIC SO S8 PART MARKING TJMAX = 125°C, θJA = 120°C/W 1317 1317B 1317I 1317BI LTHA LTHB Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS Commercial Grade VIN = 2V, VSHDN = 2V, TA = 25°C, unless otherwise noted. SYMBOL PARAMETER CONDITIONS IQ Quiescent Current Not Switching, VSHDN = 2V (LT1317) VSHDN = 0V (LT1317/LT1317B) VSHDN = 2V, Switching (LT1317B) VSHDN = 2V, Switching (LT1317B) VFB Feedback Voltage MIN ● ● µA µA mA mA 1.22 1.20 1.24 1.24 1.26 1.26 V V 12 60 nA 12 V 240 µmhos ● Input Voltage Range ● 1.5 ● 70 700 V/V ● 80 85 % 710 660 800 ● Error Amp Transconductance AV Error Amp Voltage Gain ∆I = 5µA Maximum Duty Cycle Switch Current Limit (Note 3) Burst Mode Operation Switch Current Limit 2 UNITS 160 40 6.5 7.5 FB Pin Bias Current (Note 2) gm fOSC MAX 100 25 4.8 ● ● IB TYP Switching Frequency VIN = 2.5V, Duty Cycle = 30% VIN = 2.5V, Duty Cycle = 30% Duty Cycle = 30% (LT1317) 140 1300 1350 275 ● 520 620 mA mA mA 720 kHz LT1317/LT1317B ELECTRICAL CHARACTERISTICS Commercial Grade SYMBOL VIN = 2V, VSHDN = 2V, TA = 25°C unless otherwise noted. PARAMETER CONDITIONS Shutdown Pin Current VSHDN = VIN VSHDN = 0V MIN ● ● LBI Threshold Voltage ● 190 180 TYP MAX UNITS 0.015 – 2.3 0.06 –6 µA µA 200 200 210 220 mV mV LBO Output Low ISINK = 10µA ● 0.15 0.25 V LBO Leakage Current VLBI = 250mV, VLBO = 5V ● 0.02 0.1 µA LBI Input Bias Current (Note 4) VLBI = 150mV ● 5 40 nA Low-Battery Detector Gain 1MΩ Load Switch Leakage Current VSW = 5V Switch VCE Sat ISW = 500mA 2000 ● 3 µA 300 350 400 mV mV 0.08 0.15 %/V ● Reference Line Regulation 1.8V ≤ VIN ≤ 12V ● SHDN Input Voltage High ● SHDN Input Voltage Low ● Industrial Grade 1.4 PARAMETER CONDITIONS IQ Quiescent Current Not Switching, VSHDN = 2V (LT1317) VSHDN = 0V (LT1317/LT1317B) VSHDN = 2V, Switching (LT1317B) VFB Feedback Voltage ● IB FB Pin Bias Current (Note 2) ● Input Voltage Range ● 1.7 ● 70 Error Amp Transconductance ∆I = 5µA Maximum Duty Cycle Switch Current Limit (Note 3) fOSC 6 V 0.4 V VIN = 2V, VSHDN = 2V, – 40°C ≤ TA ≤ 85°C unless otherwise noted. SYMBOL gm V/V 0.01 VIN = 2.5V, Duty Cycle = 30% Switching Frequency Shutdown Pin Current VSHDN = VIN VSHDN = 0V MIN ● ● ● 1.20 140 MAX UNITS 160 40 7.5 µA µA mA 1.26 V 80 nA 12 V 240 µmhos ● 80 ● 550 1350 mA ● 500 750 kHz 0.1 –7 µA µA 220 mV ● ● LBI Threshold Voltage TYP ● 180 % LBO Output Low ISINK = 10µA ● 0.25 V LBO Leakage Current VLBI = 250mV, VLBO = 5V ● 0.1 µA LBI Input Bias Current (Note 4) VLBI = 150mV ● 60 nA Switch Leakage Current VSW = 5V ● 3 µA Switch VCE Sat ISW = 500mA ● 400 mV Reference Line Regulation 1.8V ≤ VIN ≤ 12V ● 0.15 %/V SHDN Input Voltage High ● SHDN Input Voltage Low ● The ● denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. 1.4 6 V 0.4 V Note 2: Bias current flows into FB pin. Note 3: Switch current limit guaranteed by design and/or correlation to static tests. Duty cycle affects current limit due to ramp generator. Note 4: Bias current flows out of LBI pin. 3 LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Oscillator Frequency 1000 800 VIN = 2V L = 10µH 25°C 85°C 600 550 0 2 4 6 8 INPUT VOLTAGE 10 900 SWITCH CURRENT (mA) –40°C 650 SWITCH CURRENT (mA) OSCILLATOR FREQUENCY (kHz) 700 500 600 400 200 0 20 40 60 DUTY CYCLE (%) 800 600 MINIMUM (25°C) 400 200 20 40 60 DUTY CYCLE (%) 80 5 4 3 2 1 Feedback Voltage 0 25 50 TEMPERATURE (°C) 75 0 25 50 TEMPERATURE (°C) –40°C 300 200 100 0 75 100 1317 TPC07 0.2 0.4 0.6 0.8 SWITCH CURRENT (A) Quiescent Current, SHDN = 2V 110 202 100 201 200 199 198 197 195 –50 1 1317 TPC06 203 90 80 70 60 50 40 196 –25 25°C 400 100 QUIESCENT CURRENT (µA) LBI REFERENCE VOLTAGE (mV) 1.21 1.20 –50 500 LBI Reference Voltage 1.22 85°C 600 1317 TPC05 1.25 100 0 –25 1317 TPC04 1.23 75 700 0 –50 100 1.24 0 25 50 TEMPERATURE (°C) Switch Voltage Drop (VCESAT) SWITCH VOLTAGE (VCESAT) (mV) LBI INPUT BIAS CURRENT (nA) TYPICAL –25 1317 TPC03 6 1000 SWITCH CURRENT (mA) 100 LBI Input Bias Current 1200 FEEDBACK VOLTAGE (V) 80 1317 TPC02 Switch Current Limit 0 700 500 –50 0 12 800 600 1317 TPC01 4 Switch Current Limit, Duty Cycle = 30% Burst Mode Current Limit (LT1317) –25 0 25 50 TEMPERATURE (°C) 75 100 1317 TPC08 30 –50 –25 0 25 50 TEMPERATURE (°C) 75 100 1317 TPC09 LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Quiescent Current, SHDN = 0V SHDN Pin Current FB Pin Bias Current 26 40 2 36 24 23 22 21 32 SHDN PIN CURRENT (µA) FB PIN BIAS CURRENT (nA) QUIESCENT CURRENT (µA) 25 28 24 20 16 12 1 0 –1 –2 8 4 20 –50 –25 0 25 50 TEMPERATURE (°C) 75 0 –50 100 –3 –25 0 25 50 TEMPERATURE (°C) 1317 TPC10 0 100 80 80 80 EFFICIENCY (%) 90 EFFICIENCY (%) 90 70 60 VIN = 1.65V 50 VIN = 3V 1 10 100 LOAD CURRENT (mA) 60 VIN = 1.65V 50 VIN = 2.2V VIN = 2.2V VIN = 3V VIN = 3V 40 40 0.3 70 VIN = 1.65V 50 VIN = 2.2V 1000 1 10 100 LOAD CURRENT (mA) 1000 1 Transient Response (LT1317) Burst Mode Operation (LT1317) VOUT 100mV/DIV AC COUPLED VOUT 100mV/DIV AC COUPLED VOUT 50mV/DIV AC COUPLED IL 200mA/DIV IL 200mA/DIV IL 200mA/DIV ILOAD 165mA 5mA ILOAD 165mA 5mA VSW 5V/DIV VIN = 2V 1ms/DIV VOUT = 3.3V CIRCUIT OF FIGURE 1 WITH LT1317B 1317 TPC17 1000 1317 TPC15 Transient Response (LT1317B) 1317 TPC16 10 100 LOAD CURRENT (mA) 1317 TPC14 1317 TPC13 VIN = 2V 1ms/DIV VOUT = 3.3V CIRCUIT OF FIGURE 1 6 5 2-Cell to 5V Converter Efficiency (LT1317B) 90 60 2 4 3 SHDN PIN VOLTAGE (V) 1317 TPC12 2-Cell to 3.3V Converter Efficiency (LT1317B) 70 1 1317 TPC11 5V Output Efficiency, Circuit of Figure 1 (LT1317) EFFICIENCY (%) 75 VIN = 2V 20µs/DIV VOUT = 3.3V ILOAD = 30mA CIRCUIT OF FIGURE 1 1317 TPC18 5 LT1317/LT1317B U W TYPICAL PERFOR A CE CHARACTERISTICS Load Regulation (LT1317) Load Regulation (LT1317) VOUT 50mV/DIV DC COUPLED OFFSET ADDED Load Regulation (LT1317) VOUT 50mV/DIV DC COUPLED OFFSET ADDED VOUT 50mV/DIV DC COUPLED OFFSET ADDED VIN = 1.5V VOUT = 5V ILOAD 25mA/DIV VIN = 2V VOUT = 5V 1317 TPC19 Load Regulation (LT1317) ILOAD 25mA/DIV Load Regulation (LT1317) ILOAD 25mA/DIV 1317 TPC22 ILOAD 50mA/DIV 1317 TPC21 Load Regulation (LT1317) VOUT 50mV/DIV DC COUPLED OFFSET ADDED VOUT 50mV/DIV DC COUPLED OFFSET ADDED VIN = 1.5V VOUT = 3.3V VIN = 2.5V VOUT = 5V 1317 TPC20 VOUT 50mV/DIV DC COUPLED OFFSET ADDED VIN = 2V VOUT = 3.3V ILOAD 50mA/DIV 1317 TPC23 VIN = 2.5V VOUT = 3.3V ILOAD 50mA/DIV 1317 TPC24 Note: For load regulation pictures, double lines are due to output capacitor ESR. U U U PIN FUNCTIONS VC (Pin 1): Compensation Pin for Error Amplifier. Connect a series RC network from this pin to ground. Typical values for compensation are a 33k/3.3nF combination. A 100pF capacitor from the VC pin to ground is optional and improves noise immunity. Minimize trace area at VC. FB (Pin 2): Feedback Pin. Reference voltage is 1.24V. Connect resistor divider tap here. Minimize trace area at FB. Set VOUT according to: VOUT = 1.24V(1 + R1/R2). SHDN (Pin 3): Shutdown. Pull this pin low for shutdown mode (only the low-battery detector remains active). Leave this pin floating or tie to a voltage between 1.4V and 6V to enable the device. SHDN pin is logic level and need only meet the logic specification (1.4V for high, 0.4V for low). 6 GND (Pin 4): Ground. Connect directly to local ground plane. SW (Pin 5): Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to keep EMI down. VIN (Pin 6): Supply Pin. Must be bypassed close to the pin. LBI (Pin 7): Low-Battery Detector Input. 200mV reference. Voltage on LBI must stay between ground and 700mV. Low-battery detector remains active in shutdown mode. LBO (Pin 8): Low-Battery Detector Output. Open collector, can sink 10µA. A 1MΩ pull-up is recommended. LT1317/LT1317B W BLOCK DIAGRAM LBI 1.24V REFERENCE + gm FB 2 + 7 VC LBO 8 1 – ERROR AMPLIFIER + – 200mV A4 ENABLE SHDN VOUT BIAS R1 (EXTERNAL) – SHUTDOWN 3 A1 COMPARATOR SW FB 5 – R2 (EXTERNAL) RAMP GENERATOR + Σ + + FF Q3 Q R A2 COMPARATOR DRIVER S + A=2 600kHz OSCILLATOR 0.08Ω – 4 GND 1317 BD U W U U APPLICATIONS INFORMATION OPERATION The LT1317 combines a current mode, fixed frequency PWM architecture with Burst Mode micropower operation to maintain high efficiency at light loads. Operation can best be understood by referring to the Block Diagram. The error amplifier compares voltage at the FB pin with the internal 1.24V bandgap reference and generates an error signal VC. When VC decreases below the bias voltage on hysteretic comparator A1, A1’s output goes low, turning off all circuitry except the 1.24V reference, error amplifier and low-battery detector. Total current consumption in this state is 100µA. As output loading causes the FB voltage to decrease, VC increases causing A1’s output to go high, in turn enabling the rest of the IC. Switch current is limited to approximately 250mA initially after A1’s output goes high. If the load is light, the output voltage (and FB voltage) will increase until A1’s output goes low, turning off the rest of the LT1317. Low frequency ripple voltage appears at the output. The ripple frequency is dependent on load current and output capacitance. This Burst Mode operation keeps the output regulated and reduces average current into the IC, resulting in high efficiency even at load currents of 300µA or less. If the output load increases sufficiently, A1’s output remains high, resulting in continuous operation. When the LT1317 is running continuously, peak switch current is controlled by VC to regulate the output voltage. The switch is turned on at the beginning of each switch cycle. When the summation of a signal representing switch current and a ramp generator (introduced to avoid subharmonic oscillations at duty factors greater than 50%) exceeds the VC signal, comparator A2 changes state, resetting the flip-flop and turning off the switch. Output voltage increases as switch current is increased. The output, attenuated by a resistor divider, appears at the FB pin, closing the overall loop. Frequency compensation is provided by an external series RC network and an optional capacitor connected between the VC pin and ground. Low-battery detector A4’s open collector output (LBO) pulls low when the LBI pin voltage drops below 200mV. There is no hysteresis in A4, allowing it to be used as an amplifier in some applications. The low-battery detector remains active in shutdown. To enable the converter, SHDN must be left floating or tied to a voltage between 1.4V and 6V. 7 LT1317/LT1317B U W U U APPLICATIONS INFORMATION The LT1317B differs from the LT1317 in that the bias point on A1 is set lower than on the LT1317 so that minimum switch current can drop below 50mA. Because A1’s bias point is set lower, there is no Burst Mode operation at light loads and the device continues switching at constant frequency. This results in the absence of low frequency output voltage ripple at the expense of light load efficiency. The difference between the two devices is clearly illustrated in Figure 2. The top two traces in Figure 2 show an LT1317/LT1317B circuit, using the components indicated in Figure 1, set to a 3.3V output. Input voltage is 2V. Load current is stepped from 2mA to 200mA for both circuits. Low frequency Burst Mode operation voltage ripple is observed on Trace A, while none is observed on Trace B. TRACE A TRACE B ILOAD 1 2 8 LT1317 7 3 6 4 5 L D CIN MULTIPLE VIAs VIN COUT GND VOUT 1317 F03 Figure 3. Recommended Component Placement. Traces Carrying High Current Are Direct. Trace Area at FB Pin and VC Pin is Kept Low. Lead Length to Battery Should be Kept Short. COMPONENT SELECTION LT1317 VOUT 100mV/DIV AC COUPLED LT1317B VOUT 100mV/DIV AC COUPLED Inductors 200mA 2mA 1ms/DIV 1317 F02 Figure 2. LT1317 Exhibits Ripple at 2mA Load During Burst Mode Operation, the LT1317B Does Not LAYOUT HINTS The LT1317 switches current at high speed, mandating careful attention to layout for proper performance. You will not get advertised performance with careless layouts. Figure 3 shows recommended component placement. Follow this closely in your PC layout. Note the direct path of the switching loops. Input capacitor CIN must be placed close (< 5mm) to the IC package. As little as 10mm of wire or PC trace from CIN to VIN will cause problems such as inability to regulate or oscillation. 8 GROUND PLANE Inductors appropriate for use with the LT1317 must possess three attributes. First, they must have low core loss at 600kHz. Most ferrite core units have acceptable losses at this switching frequency. Inexpensive iron powder cores should be viewed suspiciously, as core losses can cause significant efficiency penalties at 600kHz. Second, the inductor must be able to handle peak switch current of the LT1317 without saturating. This places a lower limit on the physical size of the unit. Molded chokes or chip inductors usually do not have enough core to support the LT1317 maximum peak switch current and are unsuitable for the application. Lastly, the inductor should have low DCR (copper wire resistance) to prevent efficiency-killing I2R losses. Linear Technology has identified several inductors suitable for use with the LT1317. This is not an exclusive list. There are many magnetics vendors whose components are suitable for use. A few vendor’s components are listed in Table 1. LT1317/LT1317B U U W U APPLICATIONS INFORMATION Table 1. Inductors Suitable for Use with the LT1317 PART VALUE MAX DCR MFR HEIGHT (mm) LQH3C100 10µH 0.57 Murata-Erie 2.0 DO1608-103 10µH 0.16 Coilcraft 3.0 CD43-100 10µH 0.18 Sumida 3.2 CD54-100 10µH 0.10 Sumida 4.5 Best Efficiency CTX32CT-100 10µH 0.50 Coiltronics 2.2 1210 Footprint COMMENT Smallest Size, Limited Current Handling Capacitor Selection Low ESR (Equivalent Series Resistance) capacitors should be used at the output of the LT1317. For most applications a solid tantalum in a C or D case size works well. Acceptable capacitance values range from 10µF to 330µF with ESR falling between 0.1Ω and 0.5Ω. If component size is an issue, tantalum capacitors in smaller case sizes can be used but they have high ESR and output voltage ripple may reach unacceptable levels. Ceramic capacitors are an alternative because of their combination of small size and low ESR. A 10µF ceramic capacitor will work for some applications but the extremely low ESR of these capacitors may cause loop stability problems. Compensation components will need L1 10µH to be adjusted to ensure a stable system for the entire input voltage range. Figure 4 shows a 2V to 3.3V converter with new values for RC and CC. Figure 5 details transient response for this circuit. Also, ceramic caps are prone to temperature effects and the designer must check loop stability over the operating temperature range (see section on Frequency Compensation). Input bypass capacitor ESR is less critical and smaller units may be used. If the input voltage source is physically near the VIN pin (<5mm), a 10µF ceramic or a 10µF A case tantalum is adequate. Diodes Most of the application circuits on this data sheet specify the Motorola MBR0520L surface mount Schottky diode. In lower current applications, a 1N4148 can be used, although efficiency will suffer due to the higher forward drop. This effect is particularly noticeable at low output voltages. For higher voltage output applications, such as LCD bias generators, the extra drop is a small percentage of the output voltage so the efficiency penalty is small. The low cost of the 1N4148 makes it attractive wherever it can be used. In through hole applications the 1N5818 is the all around best choice. D1 VIN 2V VOUT 3.3V VIN SW FB LT1317B C1 10µF SHDN VC RC 20k CC 1500pF D1: MBR0520 L1: SUMIDA CD43-100 GND R1 1M 1% R2 604k 1% C2 10µF CERAMIC VOUT 200mV/DIV AC COUPLED ILOAD 5mA TO 200mA 1317 F04 Figure 4. 2V to 3.3V Converter with a 10µF Ceramic Output Capacitor. RC and CC Have Been Adjusted to Give Optimum Transient Response. 200µs/DIV 1317 F05 Figure 5. Transient Response for the Circuit of Figure 4. 9 LT1317/LT1317B U W U U APPLICATIONS INFORMATION FREQUENCY COMPENSATION 10µH The LT1317 has an external compensation pin (VC) which allows the frequency response to be optimized for the circuit configuration. In most cases, the values used in Figure 1 will work. Some circuits may need additional compensation and a simple trial and error method for determining the necessary component values is given. Figure 6 shows the test setup. A load step is applied and the resulting output voltage waveform is observed. Figures 7 through 10 detail the response for various values of R and C in the compensation network. The circuit of Figure 7 starts with a large C and small R giving a highly overdamped system. This system will always be stable but the output voltage displays a long settling time of >5ms. Figure 8’s circuit has reduced C giving a shorter settling time but still overdamped. Figure 9 shows the results when C is reduced to the point where the system becomes underdamped. The output voltage responds quickly (≈200µs to 300µs) but some ringing exists. Figure 10 has VOUT 3.3V VIN 47µF CC2 100pF 1M 15Ω 2W + 47µF GND 604k R 50Ω C 1317 F06 Figure 6. Frequency Response Test Setup optimum R and C values giving the best possible settling time with adequate phase margin. An additional 100pF capacitor (CC2) is connected to the VC pin and is necessary if the LT1317 is operated near current limit. Also, CC2 should be present when higher ESR output capacitors are used. ILOAD 2mA TO 200mA ILOAD 2mA TO 200mA 5ms/DIV 1317 F07 1317 F08 Figure 8. Reducing C to 22nF Speeds Up the Response. (R = 33k) Figure 7. With C = 56nF and R = 33k, the System is Highly Overdamped. VOUT 100mV/DIV AC COUPLED VOUT 100mV/DIV AC COUPLED ILOAD 2mA TO 200mA ILOAD 2mA TO 200mA 1317 F09 Figure 9. Using 680pF for C Results in an Underdamped System with Ringing. (R = 33k) 10 FB SHDN VC VOUT 100mV/DIV AC COUPLED 1ms/DIV SW LT1317 + VOUT 100mV/DIV AC COUPLED 5ms/DIV MBR0520L VIN 2V 1ms/DIV 1317 F10 Figure 10. 3.3nF and 33k Gives the Shortest Settling Time with No Ringing. LT1317/LT1317B U U W U APPLICATIONS INFORMATION LOW-BATTERY DETECTOR The LT1317’s low-battery detector is a simple PNP input gain stage with an open collector NPN output. The negative input of the gain stage is tied internally to a 200mV ±5% reference. The positive input is the LBI pin. Arrangement as a low-battery detector is straightforward. Figure 11 details hookup. R1 and R2 need only be low enough in value so that the bias current of the LBI pin doesn’t cause large errors. For R2, 100k is adequate. The 200mV reference can also be accessed as shown in Figure 12. The low-battery detector remains active in shutdown. 3.3V R1 VIN LBI LT1317 1M + LBO R2 100k TO PROCESSOR – 200k 200mV INTERNAL REFERENCE GND V – 200mV R1 = LB 2µA 2N3906 LT1317 VREF 200mV LBI + 10k 1317 F11 VIN LBO 10µF GND 1317 F12 Figure 11. Setting Low-Battery Detector Trip Point Figure 12. Accessing 200mV Reference U TYPICAL APPLICATIO S Single Li-Ion Cell to 3.3V SEPIC Converter C3 1µF L1A* 3.3V SEPIC Efficiency 80 MBR0520 SINGLE Li-ION CELL (2.7V TO 4.2V) C1 47µF VIN SW FB LT1317 SHDN VC GND 33k L1B* VOUT 3.3V 250mA 1M 1% + 604k 1% C2 47µF EFFICIENCY (%) 75 + 70 65 60 VIN = 2.7V VIN = 3.5V 55 VIN = 4.2V 3300pF C1, C2: AVX TPSC476M010 C3: AVX 1206YC106KAT * COILTRONICS CTX20-1 50 1317 TA03 1 10 100 LOAD CURRENT (mA) 1000 1317 TA03a 11 LT1317/LT1317B U TYPICAL APPLICATIO S 5V to 12V Boost Converter L1 22µH 5V to 12V Boost Converter Efficiency 90 MBR0520 VIN + 47µF VOUT 12V 150mA SW FB LT1317 SHUTDOWN SHDN VC 85 EFFICIENCY (%) VIN 5V 1.07M 1% LB0 GND + C2 47µF 124k 1% 56k 80 75 3300pF 70 L1: SUMIDA CD54-220 1317 TA04 10 LOAD CURRENT (mA) 1 100 1317 TA04a Single Li-Ion to 5V DC/DC Converter L1 10µH Single Li-Ion to 5V DC/DC Converter Efficiency 90 MBR0520 47µF SINGLE Li-ION CELL (2.7V TO 4.2V) VIN LT1317 SHUTDOWN SHDN VC SW FB EFFICIENCY (%) 85 + VOUT 5V 250mA 1M 1% GND + 47µF 75 70 VIN = 2.7V 324k 1% 33k 80 VIN = 3.5V 65 3300pF VIN = 4.2V 60 L1: SUMIDA CD43-100 1 1317 TA05 10 100 LOAD CURRENT (mA) 1000 1317 TA05a Low Profile 3.3 to 5V Converter L1 10µH D1 3.3V 5V 125mA VIN + C1 15µF 10V SW FB LT1317BCMS8 SHDN VC 1M GND 33k 332k C2 10µF CERAMIC 3.3nF C1: AVX TAJA156M010 C2: MURATA GRM235Y5V106Z01 L1: MURATA LQH3C100 OR SUMIDA CLQ61-100N D1: MOTOROLA MBR0520LT1 12 1317 TA06 LT1317/LT1317B U TYPICAL APPLICATIO S 2-Cell to 5V DC/DC Converter with Undervoltage Lockout L1 10µH D1 5V 130mA 301k + 100k VIN 22µF 10V LT1317 SW FB VC SHDN 2 ALKALINE CELLS LBO LBI 1M 340k 1M 1% GND 33k 332k 1% + 100µF 10V 3.3nF 470pF D1: MOTOROLA MBR0520LT1 L1: SUMIDA CD43-101 1317 TA07 STARTS AT VIN = 1.9V STOPS AT VIN = 1.6V Universal Wall Cube to 4.1V L1A 20µH VIN 1.5V TO 10V 100k + VIN 15µF 20V LT1317 SHDN VC CERAMIC 10µF, 16V D1 VOUT 4.1V 110mA SW FB L1B GND 1M 1% + Q1 432k 1% 33k 47µF 10V 3.3nF D1: MOTOROLA MBR0520LT1 L1: COILTRONICS CTX20-1 Q1: 2N3904 1317 TA08 2 Li-Ion to 8.2V DC/DC Converter L1 22µH + D1 8.2V 400mA 22µF 16V VIN SW LT1317/LT1317B 2 Li-ION CELLS (5.8V TO 8.4V) SHUTDOWN 1M + FB SHDN VC 100pF 22pF 47µF 16V GND 178k 33k 3.3nF D1: MOTOROLA MBR0520LT1 L1: SUMIDA CD43-220 1317 TA09 13 LT1317/LT1317B U TYPICAL APPLICATIO S Single Li-Ion Cell to 4V/70mA, – 4V/10mA D2 4.5V TO 2.5V 1µF CERAMIC VIN SW LT1317 Li-Ion CELL SHUTDOWN SHDN VC + 1µF CERAMIC L1 22µH – 4V 10mA C3 15µF C1 1µF L2 22µH D1 1.00M 4V 70mA FB GND + 100pF 33k 442k C2 33µF 3.3nF C1: MURATA GRM235Y5V107Z01 C2: AVX TAJB336M010 C3: AVX TAJA156M010 D1: MBR0520 D2: BAT54S (DUAL DIODE) L1, L2: MURATA LQH3C220K04 1317 TA02 Low Noise 33V Varactor Bias Supply D3 680Ω 150pF D2 L1 22µH C3 0.1µF D1 VIN 3V TO 6V VIN + C1 15µF 10V SW FB 150k 47Ω VOUT 33V 0mA TO 10mA LT1317B GND VC 33k C4 0.1µF 5.9k + C2 10µF 35V C5 0.1µF C6 0.1µF 3300pF C1: AVX TAJ156M010 C2: SANYO 35CV33GX C3, C4, C5, C6: 0.1µF CERAMIC D1, D2, D3: MOTOROLA MMBD914LT1 L1: MURATA LQH3C220 14 1317 TA11 LT1317/LT1317B U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.118 ± 0.004* (3.00 ± 0.102) 8 7 6 5 0.118 ± 0.004** (3.00 ± 0.102) 0.192 ± 0.004 (4.88 ± 0.10) 1 2 3 4 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.034 ± 0.004 (0.86 ± 0.102) 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) TYP 0.021 ± 0.006 (0.53 ± 0.015) 0.006 ± 0.004 (0.15 ± 0.102) MSOP (MS8) 1197 * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 0.014 – 0.019 (0.355 – 0.483) 0.050 (1.270) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 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. SO8 0996 15 LT1317/LT1317B U TYPICAL APPLICATION Digital Camera Power Supply 10k 24V D3 T1 7 + LC 8 18V 3mA C5 10µF 35V D2 5 + LB 6 LPRI:15µH + C1 22µF 10V 4 AA CELLS (3.2V TO 6.5V) SHUTDOWN 2 D1 3 + LA 1 4 C3 1µF, 16V VIN 5V 20mA C4 22µF 10V C2 100µF 6V 3.3V 150mA SW LT1317 SHDN 1M FB GND VC 10k 604k 3300pF 1317 TA10 C1, C4: AVX TPSC226M016 C2: AVX TPSC106M006 C3: CERAMIC (i.e. AVX, MANY OTHERS) C5: SANYO 35CV10GX D1, D2: MBR0520LT1 (MOTOROLA) OR EQUIVALENT D3: MMBD914LT1 (MOTOROLA) OR EQUIVALENT T1: COILTRONICS CTX02-14272-X1 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC 1163 Triple High Side Driver for 2-Cell Inputs 1.8V Minimum Input, Drives N-Channel MOSFETs LTC1174 Micropower Step-Down DC/DC Converter 94% Efficiency, 130µA IQ, 9V to 5V at 300mA LT1302 High Output Current Micropower DC/DC Converter 5V/600mA from 2V, 2A Internal Switch, 200µA IQ LT1304 2-Cell Micropower DC/DC Converter Low-Battery Detector Active in Shutdown LT1307 Single Cell Micropower 600kHz PWM DC/DC Converter 3.3V at 75mA from 1 Cell, MSOP Package LTC1440/1/2 Ultralow Power Single/Dual Comparators with Reference 2.8µA IQ, Adjustable Hysteresis LTC1516 2-Cell to 5V Regulated Charge Pump 12µA IQ, No Inductors, 5V at 50mA from 3V Input LT1521 Micropower Low Dropout Linear Regulator 500mV Dropout, 300mA Current, 12µA IQ ® 16 Linear Technology Corporation 13177bf LT/TP 1198 4K • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1998