LT1931 LINER
Document overview
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Technical content
switches at 1.2MHz while the LT1931A switches at 2.2MHz. can be achieved when ceramic output capacitors are used. IN to VOUT differential of up to 34V. , LTC and LT are registered trademarks of Linear Technology Corporation. Figure 1. 5V to –5V, 350mA Inverting DC/DC Converter
1931 F01
1931 TA01
ThinSOT is a trademark of Linear Technology Corporation.
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS Minimum Operating Voltage 2.45 2.6 2.45 2.6 V Maximum Operating Voltage 16 16 V NFB Pin Bias Current V NFB = –1.255V l 48 8 1 6 mA Quiescent Current V SHDN = 2.4V, Not Switching 4.2 6 5.8 8 mA Quiescent Current in Shutdown V SHDN = 0V, VIN = 3V 0.01 1 0.01 1 mA l 0.85 1.6 1.6 2.9 MHz Maximum Duty Cycle l 84 90 75 82 % Switch Current Limit (Note 3) 1 1.2 2 1 1.2 2.5 A Switch VCESAT ISW = 1A 400 600 400 600 mV Switch Leakage Current V SW = 5V 0.01 1 0.01 1 mA SHDN Input Voltage, High 2.4 2.4 V SHDN Input Voltage, Low 0.5 0.5 V SHDN Pin Bias Current V SHDN = 3V 16 32 35 70 mA VSHDN = 0V 0 0.1 0 0.1 mA TJMAX = 125°C, qJA = 256°C/ W ORDER PART NUMBER (Note 1) Operating Temperature Range (Note 2) .. – 40°C to 85°C LT1931ES5 LT1931AES5 ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W The l denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 3V, VSHDN = VIN, unless otherwise noted. (Note 2) SW 1 GND 2 TOP VIEW S5 PACKAGE 5-LEAD PLASTIC SOT-23 NFB 3
5 VIN
4 SHDN
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1931E/LT1931AE are guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the – 40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Current limit guaranteed by design and/or correlation to static test. Consult factory for parts specified with wider operating temperature ranges.
TYPICAL PERFOR A CE CHARACTERISTICS UW Quiescent Current TEMPERATURE (°C) –50 QUIESCENT CURRENT (mA) 4.5 5.0 5.5 25 75
1931 G01
4.0 3.5 3.0 –25 0 50 6.0 6.5 7.0 100 NOT SWITCHING LT1931A LT1931 TEMPERATURE (°C) –50 –1.28 –1.27 –1.26 –1.25 –1.24 –1.22 –25 02 5 5 0
1931 G02
–1.23FEEDBACK VOLTAGE (V) SHDN PIN VOLTAGE (V) –10 SHDN PIN CURRENT (µA) 1 2 34
1931 G03
TA = 25°C LT1931 Feedback Pin Voltage Shutdown Pin Current Current Limit Switch Saturation Voltage Oscillator Frequency DUTY CYCLE (%) CURRENT LIMIT (A) 0.8 1.2
1931 G04
0.4 30 50 7020 40 60 80 1.6 0.6 1.0 0.2 1.4 TA = 25°C SWITCH CURRENT (A) VCESAT (V) 0.05 0.15 0.20 0.25 0.8 0.45
1931 G05
0.10 0.30 0.35 0.40 TA = 25°C TEMPERATURE (°C) –50 0.5 FREQUENCY (MHz) 0.9 1.3 1.7 –25 0 25 50
1931 G06
2.1 2.5 0.7 1.1 1.5 1.9 2.3 100 LT1931A LT1931 UUUPI FU CTIO S SW (Pin 1): Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to keep EMI down. GND (Pin 2): Ground. Tie directly to local ground plane. NFB (Pin 3): Feedback Pin. Reference voltage is –1.255V. Connect resistive divider tap here. Minimize trace area. The NFB bias current flows out of the pin. Set R1 and R2 according to: For LT R V R OUT1931 1 1 255 1 255 2 41 0 6 : || ± . . · ± + () For LT A R V R OUT1931 1 1 255 1 255 2 81 0 6 : || ± . . · ± + () SHDN (Pin 4): Shutdown Pin. Tie to 2.4V or more to enable device. Ground to shut down. VIN (Pin 5): Input Supply Pin. Must be locally bypassed.
The LT1931 uses a constant frequency, current mode control scheme to provide excellent line and load regula- tion. Operation can be best understood by referring to the Block Diagram in Figure 2. At the start of each oscillator cycle, the SR latch is set, turning on the power switch Q3. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the PWM comparator A2. When this voltage exceeds the level at the negative input of A2, the SR latch is reset, turning off the power switch. The level at the negative input of A2 is set by the error amplifier (g m) and is simply an amplified version of the difference between the feedback voltage and the reference voltage of –1.255V. In this manner, the error amplifier sets the correct peak current level to keep the output in regulation. If the error amplifier’s output increases, more current is taken from the output; if it decreases, less current is taken. One function not shown in Figure 2 is the current limit. The switch current is constantly monitored and not allowed to exceed the nominal value of 1.2A. If the switch current reaches 1.2A, the SR latch is reset regardless of the state of comparator A2. This current limit protects the power switch as well as various external components connected to the LT1931. The Block Diagram for the LT1931A is identical except that the oscillator is 2.2MHz and resistors R3 to R6 are one-half the LT1931 values. + – LATCH RQ S 0.01Ω SW DRIVER COMPARATOR 2SHUTDOWN SHDN SRAMP GENERATOR RC CC 1.2MHz OSCILLATOR GND 1931 BD 80k 150k 30k x10 80k VINVIN 5 NFB CPL (OPTIONAL) (EXTERNAL) (EXTERNAL) VOUT NFB gm
LT1931. Care must be taken in deciding which part to use. the actual duty cycle is reduced. in Table 1 and those for the LT1931A are listed in Table 2. will usually be the best choice for most LT1931 designs. case, the inductor must carry the entire 1A switch current. Table 1. Recommended Inductors—LT1931 Table 2. Recommended Inductors—LT1931A
percentage points increase in efficiency. be used at the output to minimize the output ripple voltage. a 4.7mF to 10 mF capacitor will suffice for the LT1931A. Table 3. Ceramic Capacitor Manufacturers implies that the ESR zero is improving the phase margin. Figure 3. Transient Response of Inverting Converter
Figure 4. Transient Response of Inverting Converter Figure 5. Transient Response of Inverting Converter with 22mF
1931 F07
Figure 7. RSS and CSS at SHDN Pin Provide Soft-Start to LT1931 Inverting Converter Figure 6. Start-Up Waveforms for 5V to – 5V Application
be increased further for an even slower ramp, if desired.
1931 F10
Figure 8. RSS = 15k, CSS = 33nF; VOUT Reaches – 5V in 1ms; Figure 9. RSS = 15k, CSS = 68nF; VOUT Reaches – 5V in 1.6ms; Figure 10. Suggested Component Placement. LT1931A. The Motorola MBR0520 is a very good choice. 0.5A, a Microsemi UPS5817 rated at 1A is recommended.
–12V 150mA
1931 TA02
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R TMK316BJ105ML C3: TAIYO YUDEN X5R EMK325BJ106MM D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLS62-100 4.7µF C3 10mF 1µF 10k 84.5k NFB SHDN 5V to –12V Inverting Converter LOAD CURRENT (mA) EFFICIENCY (%) 25 50 75 100
1931 TA03
–5V 300mA
1931 TA04
C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ226MM D1: ON SEMICONDUCTOR MBR0520 L1, L2: MURATA LQH3C100K04 4.7µF C3 22mF 1µF 10k 29.4k 220pF NFB SHDN 5V to – 5V Inverting Converter Using Uncoupled Inductors VIN VIN VOUT –5V 300mA
1931 TA05a
4.7mH 4.7mH GND LT1931A C1: TAIYO YUDEN X5R JMK212BJ475MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1, L2: MURATA LQH3C4R7M24 4.7µF C3 4.7mF 1µF 10k 28.7k 180pF NFB SHDN LOAD CURRENT (mA) EFFICIENCY (%) 100 200 250
1931 TA05b
2.2MHz, 5V to – 5V Inverting Converter Efficiency
–5V 200mA
1931 TA06a
3.3mH 3.3mH GND LT1931A C1: TAIYO YUDEN X5R JMK212BJ225MG C2: TAIYO YUDEN X5R LMK212BJ105MG C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1, L2: PANASONIC ELJPC3R3MF 2.2µF C3 4.7mF 1µF 10k 28.7k 68pF NFB SHDN LOAD CURRENT (mA) EFFICIENCY (%) 50 100 150 200
1931 TA06b
2.2MHz, 5V to –5V Converter Uses Tiny Chip Inductors Efficiency VIN VIN 12V VSS SW 22µH GND LT1931 NFBSHDN RSS 15k 25.5k 2.7k 1000pF CSS 68nF 4.7µF 16V 1µF 35V *TOTAL OUTPUT POWER NOT TO EXCEED 3.3W C1 TO C5: X5R OR X7R D1, D2: BAV99 OR EQUIVALENT L1: SUMIDA CR43-220 4.7µF 35V
1931 TA08
4.7µF 35V VOUT1 –33V 100mA* COM VOUT2 –66V 48mA* 1µF 35V SLIC Power Supply with – 33V and – 68V Outputs, Uses Soft-Start
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. SLIC Power Supply with – 21.6V and – 65V Outputs, Uses Soft-Start TYPICAL APPLICATIO SU VIN VIN VSS SW 10µH GND LT1931 NFBSHDN RSS 15k 16.2k 2.7k 1000pF 4.7µF 16V CSS 68nF 1µF 35VC4 1µF 35V *TOTAL OUTPUT POWER NOT TO EXCEED 1.3W C1 TO C7: X5R OR X7R D1, D2: BAV99 OR EQUIVALENT L1: SUMIDA CR43-100 4.7µF 25V 4.7µF 25V
1931 TA09
4.7µF 25V VOUT1 –21.6V 48mA* COM VOUT2 – 65V 20mA* 1µF 35V 5-Lead Plastic SOT-23 (LTC DWG # 05-08-1633) (LTC DWG # 05-08-1635) L DATUM ‘A’ .09 – .20 (.004 – .008) (NOTE 2) S5 SOT-23 0501 1.50 – 1.75 (.059 – .069) (NOTE 3) 2.60 – 3.00 (.102 – .118) .25 – .50 (.010 – .020) (5PLCS, NOTE 2) PIN ONE 2.80 – 3.10 (.110 – .118) (NOTE 3) .95 (.037) REF A A2 1.90 (.074) REF .20 (.008) .90 – 1.45 (.035 – .057) SOT-23 (Original) .00 – .15 (.00 – .006) .90 – 1.30 (.035 – .051) .35 – .55 (.014 – .021)
1.00 MAX
(.039 MAX) SOT-23 (ThinSOT) A L .01 – .10 (.0004 – .004) .80 – .90 (.031 – .035) .30 – .50 REF (.012 – .019 REF) MILLIMETERS (INCHES) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE 4. DIMENSIONS ARE INCLUSIVE OF PLATING 5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 6. MOLD FLASH SHALL NOT EXCEED .254mm 7. PACKAGE EIAJ REFERENCE IS: SC-74A (EIAJ) FOR ORIGINAL JEDEL MO-193 FOR THIN
1931f LT/TP 0601 2K • PRINTED IN USA ª LINEAR TECHNOLOGY CORPORATION 2000 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear-tech.com RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1307 Single Cell Micropower 600kHz PWM DC/DC Converter 3.3V at 75mA from One Cell, MSOP Package LT1316 Burst Mode TM Operation DC/DC with Programmable Current Limit 1.5V Minimum, Precise Control of Peak Current Limit LT1317 2-Cell Micropower DC/DC with Low-Battery Detector 3.3V at 200mA from Two Cells, 600kHz Fixed Frequency LT1610 Single Cell Micropower DC/DC Converter 3V at 30mA from 1V, 1.7MHz Fixed Frequency LT1611 Inverting 1.4MHz Switching Regulator in 5-Lead ThinSOT –5V at 150mA from 5V Input. Tiny SOT-23 Package LT1613 1.4MHz Switching Regulator in 5-Lead ThinSOT 5V at 200mA from 3.3V Input. Tiny SOT-23 Package LT1615 Micropower Constant Off-Time DC/DC Converter in 5-Lead ThinSOT 20V at 12mA from 2.5V. Tiny SOT-23 Package LT1617 Micropower Inverting DC/DC Converter in 5-Lead ThinSOT –15V at 12mA from 2.5V. Tiny SOT-23 Package LT1930/LT1930A 1.2MHz/2.2MHz, 1A Switching Regulators in 5-Lead ThinSOT 5V at 450mA from 3.3V Input. Tiny SOT-23 Package Burst Mode operation is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO U 2.2MHz, 12V to – 5V Converter Uses Low Profile Coupled Inductor Efficiency VIN VIN 12V VOUT –5V 450mA
1931 TA07a
4.7mH L1B 4.7mH GND LT1931A C1: TAIYO YUDEN Y5V EMK212F225ZG C2: 0.1µF 25V X5R C3: TAIYO YUDEN X5R JMK212BJ475MG D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CLQ4D10-4R7 DRAWING #5382-T039 2.2µF C3 4.7mF 0.1µF 10k 28.7k NFB SHDN LOAD CURRENT (mA) EFFICIENCY (%) 100 200 300 400