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LT1614 Inverting 600kHz Switching Regulator
FEATURES
s s s s s s s s s
DESCRIPTIO
Better Regulation Than a Charge Pump 0.1 Effective Output Impedance - 5V at 200mA from a 5V Input 600kHz Fixed Frequency Operation Operates with VIN as Low as 1V 1mA Quiescent Current Low Shutdown Current: 10A Low-Battery Detector Low VCESAT Switch: 295mV at 500mA
The LT (R)1614 is a fixed frequency, inverting mode switching reglator that operates from an input voltage as low as 1V. Utilizing a low noise topology, the LT1614 can generate a negative output down to - 24V from a 1V to 5V input. Fixed frequency switching ensures a clean output free from low frequency noise. The device contains a lowbattery detector with a 200mV reference and shuts down to less than 10A. No load quiescent current of the LT1614 is 1mA and the internal NPN power switch handles a 500mA current with a voltage drop of just 295mV. High frequency switching enables the use of small inductors and capacitors. Ceramic capacitors can be used in many applications, eliminating the need for bulky tantalum types. The LT1614 is available in 8-lead MSOP or SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s s s s
MR Head Bias LCD Bias GaAs FET Bias Positive-to-Negative Conversion
TYPICAL APPLICATIO
L1 22H C3 1F
VIN 5V
L2 22H
5V to - 5V Converter Efficiency
90
+
VIN C1 33F 100k 1nF
SW 69.8k D1 24.9k
EFFICIENCY (%)
C1, C2: AVX TAJB336M010 C3: TAIYO YUDEN EMK316BJ105MF D1: MBR0520 L1, L2: MURATA LQH3C220
Figure 1. 5V to - 5V/200mA Converter
+
SHDN LT1614 VC NFB GND
VOUT - 5V 200mA C2 33F
80
70
60
1614 TA01
50
40 3 100 10 30 LOAD CURRENT (mA) 300
1614 TA02
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1
LT1614 ABSOLUTE AXI U RATI GS
VIN, SHDN, LBO Voltage ......................................... 12V SW Voltage ............................................... - 0.4V to 30V NFB Voltage ............................................................ - 3V VC Voltage ................................................................ 2V LBI Voltage ............................................ 0V VLBI 1V Current into FB Pin .............................................. 1mA Junction Temperature ...........................................125C
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW NFB VC SHDN GND 1 2 3 4 8 7 6 5 LBO LBI VIN SW TOP VIEW
LT1614CMS8 LT1614IMS8
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 160C/W
MS8 PART MARKING LTID LTJB
Consult factory for Military grade parts.
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Commercial Grade 0C to 70C. VIN = 1.5V, VSHDN = VIN unless otherwise noted.
PARAMETER Quiescent Current VSHDN = 0V Feedback Voltage NFB Pin Bias Current (Note 3) Reference Line Regulation Minimum Input Voltage Maximum Input Voltage Error Amp Transconductance Error Amp Voltage Gain Switching Frequency Maximum Duty Cycle
q q q q
ELECTRICAL CHARACTERISTICS
CONDITIONS
VNFB = -1.24V 1V VIN 2V 2V VIN 6V
I = 5A 500 73 70 0.75
Switch Current Limit (Note 4)
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W
WW
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W
(Note 1)
Operating Temperature Range LT1614C ................................................. 0C to 70C LT1614I ............................................. - 40C to 85C Extended Commercial Temperature Range (Note 2) .................. - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER
NFB 1 VC 2 SHDN 3 GND 4 8 7 6 5 LBO LBI VIN SW
LT1614CS8 LT1614IS8
S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125C, JA = 120C/W
S8 PART MARKING 1614 1614I
MIN
TYP 1 5
MAX 2 10 - 1.27 -7 1.1 0.8 1 6
UNITS mA A V A %/V %/V V V mhos V/V
- 1.21 - 2.5
- 1.24 - 4.5 0.6 0.3 0.92 16 100 600 80 80 1.2
q
750
kHz % % A
LT1614
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. Commercial Grade 0C to 70C. VIN = 1.5V, VSHDN = VIN unless otherwise noted.
PARAMETER Switch VCESAT Shutdown Pin Current LBI Threshold Voltage
q
ELECTRICAL CHARACTERISTICS
CONDITIONS ISW = 500mA (25C, 0C) ISW = 500mA (70C) VSHDN = VIN VSHDN = 0V
MIN
TYP 295 10 -5
MAX 350 400 20 - 10 210 215 0.25 0.1 50 3
UNITS mV mV A A mV mV V A nA V/V A
190 185
200 0.1 0.01 10 1000 0.01
LBO Output Low LBO Leakage Current LBI Input Bias Current (Note 5) Low-Battery Detector Gain Switch Leakage Current
ISINK = 10A VLBI = 250mV, VLBO = 5V VLBI = 150mV 1M Load VSW = 5V
Industrial Grade - 40C to 85C. VIN = 1.5V, VSHDN = VIN unless otherwise noted.
PARAMETER Quiescent Current VSHDN = 0V Feedback Voltage NFB Pin Bias Current (Note 3) Reference Line Regulation Minimum Input Voltage Maximum Input Voltage Error Amp Transconductance Error Amp Voltage Gain Switching Frequency Maximum Duty Cycle Switch Current Limit (Note 4) Switch VCESAT Shutdown Pin Current LBI Threshold Voltage LBO Output Low LBO Leakage Current LBI Input Bias Current (Note 5) Low-Battery Detector Gain Switch Leakage Current ISINK = 10A VLBI = 250mV, VLBO = 5V VLBI = 150mV 1M Load VSW = 5V ISW = 500mA (- 40C) ISW = 500mA (85C) VSHDN = VIN VSHDN = 0V
q q q q
CONDITIONS
MIN
TYP 1 5
MAX 2 10 - 1.27 - 7.5 1.1 0.8 1.25 1.0 6
UNITS mA A V A %/V %/V V V V mhos V/V
- 1.21 -2
- 1.24 - 4.5 0.6 0.3 1.1 0.8
VNFB = - 1.24V 1V VIN 2V 2V VIN 6V - 40C 85C
q
q
I = 5A 500 70 0.75
16 100 600 80 1.2 250 330 10 -5 180 200 0.1 0.1 5 1000 0.01 3 350 400 20 - 10 220 0.25 0.3 30 750
kHz % A mV mV A A mV V A nA V/V A
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1614C is guaranteed to meet specified performance from 0C to 70C and is designed, characterized and expected to meet these extended temperature limits, but is not tested at - 40C and 85C. The LT1614I is guaranteed to meet the extended temperature limits.
Note 3: Bias current flows out of NFB pin. Note 4: Switch current limit guaranteed by design and/or correlation to static tests. Duty cycle affects current limit due to ramp generator. Note 5: Bias current flows out of LBI pin.
3
LT1614 TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current in Shutdown
10 10
QUIESCENT CURRENT (A)
SHDN BIAS CURRENT (A)
8
LBI BIAS CURRENT (nA)
6
4
2
0
0
1
2 3 INPUT VOLTAGE (V)
Switch VCESAT vs Current
500 TA = 25C 210 208
REFERENCE VOLTAGE (mV)
400 VCESAT (mV)
300
202 200 198 196 194 192
FREQUENCY (kHz)
200
100
0
0
100
500 200 300 400 SWITCH CURRENT (mA)
Quiescent Current vs Temperature*
6 5 4 3 VIN = 3V 2 1 0 -40 VIN = 1.25V
NFB PIN BIAS CURRENT (A)
QUIESCENT CURRENT (mA)
VNFB (V)
-20
0 20 40 TEMPERATURE (C)
*Includes diode leakage
4
UW
4 5
1614 G01
Shutdown Pin Bias Current vs Input Voltage
16 14 8 12 10 8 6 4 2 0 0 1 2 3 INPUT VOLTAGE (V) 4 5
1614 G02
LBI Bias Current vs Temperature
6
4
2
0 -50
-25
0 50 25 TEMPERATURE (C)
75
100
1614 G03
LBI Reference vs Temperature
900
Oscillator Frequency vs Input Voltage
206 204
800 85C 700
25C
-40C 600
500
600
190 -50
-25
25 50 0 TEMPERATURE (C)
75
100
1614 G05
400
1
2
3 INPUT VOLTAGE (V)
4
5
1614 G06
1614 G04
NFB Pin Bias Current vs Temperature
6 5 4 3 2 -1.220 1 0 -50 -1.215 -1.245 -1.240 -1.235 -1.230 -1.225
VNFB vs Temperature
VIN = 5V
60
80
1614 G07
-25
0 25 50 TEMPERATURE (C)
75
100
1614 G08
-1.210 -50
-25
0 25 50 TEMPERATURE (C)
75
100
1614 G09
LT1614
PIN FUNCTIONS
NFB (Pin 1): Negative Feedback Pin. Reference voltage is - 1.24V. Connect resistive divider tap here. The suggested value for R2 is 24.9k. Set R1 and R2 according to: GND (Pin 4): Ground. Connect directly to local ground plane. SW (Pin 5): Switch Pin. Minimize trace area at this pin to keep EMI down. VIN (Pin 6): Supply Pin. Must have 1F ceramic bypass capacitor right at the pin, connected directly to ground. LBI (Pin 7): Low-Battery Detector Input. 200mV reference. Voltage on LBI must stay between ground and 700mV. Float this pin if not used. LBO (Pin 8): Low-Battery Detector Output. Open collector, can sink 10A. A 1M pull-up is recommended. Float this pin if not used. The low-battery detector is disabled when SHDN is low. LBO is high-Z in this state.
R1 =
| VOUT | - 1.24 1.24 + 4.5 * 10 - 6 R2
VC (Pin 2): Compensation Pin for Error Amplifier. Connect a series RC from this pin to ground. Typical values are 100k and 1nF. Minimize trace area at VC. SHDN (Pin 3): Shutdown. Ground this pin to turn off switcher. Must be tied to VIN (or higher voltage) to enable switcher. Do not float the SHDN pin.
BLOCK DIAGRAM
VIN 6 R5 40k
Q1
VOUT R1 (EXTERNAL) NFB R2 (EXTERNAL)
NFB
RAMP GENERATOR
600kHz OSCILLATOR
Figure 2. Block Diagram
+
+ +
-
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VIN R6 40k
+
gm
VC 2 LBI
SHDN SHUTDOWN 3
-
Q2 x10 R3 30k R4 140k 1 ERROR AMPLIFIER A1 BIAS
+
ENABLE
7
+ -
A4
LBO 8
-
200mV
COMPARATOR FF R A2 S Q DRIVER
SW 5 Q3
+
A=3 0.15
-
4 GND
1614 BD
5
LT1614
OPERATIO
The LT1614 combines a current mode, fixed frequency PWM architecture with a -1.23V reference to directly regulate negative outputs. Operation can be best understood by referring to the block diagram of Figure 2. Q1 and Q2 form a bandgap reference core whose loop is closed around the output of the converter. The driven reference point is the lower end of resistor R4, which normally sits at a voltage of -1.23V. As the load current changes, the NFB pin voltage also changes slightly, driving the output of gm amplifier A1. Switch current is regulated directly on a cycle-to-cycle basis by A1's output. The flip-flop is set at the beginning of each cycle, turning on the switch. 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 stage, resetting the flipflop and turning off the switch. Output voltage decreases (the magnitude increases) as switch current is increased. The output, attenuated by external resistor divider R1 and R2, appears at the NFB pin, closing the overall loop. Frequency compensation is provided externally by a series RC connected from the VC pin to ground. Typical values are 100k and 1nF. Transient response can be tailored by adjustment of these values. As load current is decreased, the switch turns on for a shorter period each cycle. If the load current is further decreased, the converter will skip cycles to maintain output voltage regulation.
VIN
+
C1 SHUTDOWN
10Ok 1nF
GND
R2 10k
10Ok 1nF
1614 F03
GND
R2 10k
Figure 3. Direct Regulation of Negative Output Using Boost Converter with Charge Pump
Figure 4. L2 Replaces D2 to Make Low Output Ripple Inverting Topology. Coupled or Uncoupled Inductors Can Be Used. Follow Phasing If Coupled for Best Results
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The LT1614 can work in either of two topologies. The simpler topology appends a capacitive level shift to a boost converter, generating a negative output voltage, which is directly regulated. The circuit schematic is detailed in Figure 3. Only one inductor is required, and the two diodes can be in a single SOT-23 package. Output noise is the same as in a boost converter, because current is delivered to the output only during the time when the LT1614's internal switch is on. If D2 is replaced by an inductor, as shown in Figure 4, a higher performance solution results. This converter topology was developed by Professor S. Cuk of the California Institute of Technology in the 1970s. A low ripple voltage results with this topology due to inductor L2 in series with the output. Abrupt changes in output capacitor current are eliminated because the output inductor delivers current to the output during both the off-time and the on-time of the LT1614 switch. With proper layout and high quality output capacitors, output ripple can be as low as 1mVP-P. The operation of Cuk's topology is shown in Figures 5 and 6. During the first switching phase, the LT1614's switch, represented by Q1, is on. There are two current loops in operation. The first loop begins at input capacitor C1, flows through L1, Q1 and back to C1. The second loop flows from output capacitor C3, through L2, C2, Q1 and back to C3. The output current from RLOAD is supplied by L2 and C3. The voltage at node SW is VCESAT and at node SWX the voltage is -(VIN + |VOUT|). Q1 must conduct both L1 and L2 current. C2 functions as a voltage level shifter, with an approximately constant voltage of (VIN + |VOUT|) across it.
L1 VIN D1 VIN LT1614 SHDN VC NFB R1 C3 SW -VOUT SHUTDOWN C2 1F L2 L1 C2 1F D2
+
C1
D1 VIN LT1614 SHDN VC NFB R1 C3 SW -VOUT
1614 F04
LT1614
OPERATIO
When Q1 turns off during the second phase of switching, the SWX node voltage abruptly increases to (VIN + |VOUT|). The SW node voltage increases to VD (about 350mV). Now current in the first loop, begining at C1, flows through L1, C2, D1 and back to C1. Current in the second loop flows from C3 through L2, D1 and back to C3. Load current continues to be supplied by L2 and C3. An important layout issue arises due to the chopped nature of the currents flowing in Q1 and D1. If they are both tied directly to the ground plane before being combined, switching noise will be introduced into the ground plane. It is almost impossible to get rid of this noise, once present in the ground plane. The solution is to tie D1's cathode to the ground pin of the LT1614 before the combined curVCESAT L1 VIN SW -(VIN + VOUT) C2 SWX
+
C1
Figure 5. Switch-On Phase of Inverting Converter. L1 and L2 Current Have Positive dI/dt
VIN + VOUT+ VD L1 VIN SW C2 VD SWX L2 -VOUT
+
C1
Q1
D1 C3 RLOAD
Figure 6. Switch-Off Phase of Inverting Converter. L1 and L2 Current Have Negative dI/dt
+
+
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rents are dumped into the ground plane as drawn in Figures 4, 5 and 6. This single layout technique can virtually eliminate high frequency "spike" noise so often present on switching regulator outputs. Output ripple voltage appears as a triangular waveform riding on VOUT. Ripple magnitude equals the ripple current of L2 multiplied by the equivalent series resistance (ESR) of output capacitor C3. Increasing the inductance of L1 and L2 lowers the ripple current, which leads to lower output voltage ripple. Decreasing the ESR of C3, by using ceramic or other low ESR type capacitors, lowers output ripple voltage. Output ripple voltage can be reduced to arbitrarily low levels by using large value inductors and low ESR, high value capacitors.
L2 -VOUT Q1 D1 C3 RLOAD
1614 F05 1614 F06
7
LT1614
OPERATIO
Transient Response The inverting architecture of the LT1614 can generate a very low ripple output voltage. Recently available high value ceramic capacitors can be used successfully in LT1614 designs. The addition of a phase lead capacitor, CPL, reduces output perturbations due to load steps when lower value ceramic capacitors are used and connected in parallel with feedback resistor R1. Figure 7 shows an LT1614 inverting converter with resistor loads RL1 and RL2. RL1 is connected across the output, while RL2 is switched in externally via a pulse generator. Output voltage waveforms are pictured in subsequent figures, illustrating the performance of output capacitor type. Figure 8 shows the output voltage with a 50mA to 200mA load step, using an AVX TAJ "B" case 33F tantalum capacitor at the output. Output perturbation is approximately 250mV as the load changes from 50mA to 200mA. Steady-state ripple voltage is 40mVP-P, due to L1's ripple current and C3's ESR. Figure 9 pictures the output voltage and switch pin voltage at 500ns per division. Note the absence of high frequency spikes at the output. This is easily repeatable with proper layout, described in the next section.
VIN 5V VIN
L1 22H
+
C1 RC
SHDN LT1614 VC GND CC NFB
R2 24.9k
C1: AVX TAJB226M010 C2: TAIYO YUDEN LMK212BJ105MG C3: AVX TAJB336M006 OR MURATA (SEE TEXT) D1: MBR0520 L1, L2: MURATA LQH3C220
Figure 7. Switching RL2 Provides 50mA to 200mA Load Step for LT1614 5V to - 5V Converter
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In Figure 10, output capacitor C3 is replaced by a ceramic unit. These large value capacitors have ESR of 2m or less and result in very low output ripple. A 1nF capacitor, CPL, connected across R1 reduces output perburbation due to load step. This keeps the output voltage within 5% of steady-state value. Figure 11 pictures the output and switch nodes at 500ns per division. Output ripple is about 5mVP-P. Again, good layout is essential to achieve this low noise performance. Layout The LT1614 switches current at high speed, mandating careful attention to layout for best performance. You will not get advertised performance with careless layout. Figure 12 shows recommended component placement. Follow this closely in your printed circuit layout. The cut ground copper at D1's cathode is essential to obtain the low noise achieved in Figures 10 and 11's oscillographs. Input bypass capacitor C1 should be placed close to the LT1614 as shown. The load should connect directly to output capacitor C2 for best load regulation. You can tie the local ground into the system ground plane at C3's ground terminal. COMPONENT SELECTION
C2 1F L2 22H
Inductors
-VOUT RL2 33
D1 SW R1 69.8k CPL 1nF C3
RL1 100
1614 F07
Each of the two inductors used with the LT1614 should have a saturation current rating (where inductance is approximately 70% of zero current inductance) of approximately 0.4A or greater. If the device is used in "charge pump" mode, where there is only one inductor, then its rating should be 0.75A or greater. DCR of the inductors should be 0.4 or less. 22H inductors are called out in the applications schematics because these Murata units are physically small and inexpensive. Increasing the inductance will lower ripple current, increasing available output current. A coupled inductor of 33H, such as Coiltronics CTX33-2, will provide 290mA at - 5V from a 5V input. Inductance can be reduced if operating from a supply voltage below 3V. Table 1 lists several inductors that will work with the LT1614, although this is not an exhaustive list. There are many magnetics vendors whose components are suitable.
LT1614
OPERATIO
VOUT 100mV/DIV AC COUPLED
ILOAD
200mA 50mA 500s/DIV
1614 F08
Figure 8. Load Step Response of LT1614 with 33F Tantalum Output Capacitor
VOUT 100mV/DIV AC COUPLED
ILOAD
200mA 50mA 500s/DIV
1614 F10
Figure 10. Replacing C3 with 22F Ceramic Capacitor Lowers Output Voltage Ripple. 1nF Phase-Lead Capacitor in Parallel with R1 Lowers Transient Excursion
C3 C2 L2
1614 F12
Figure 12. Suggested Component Placement. Note: Cut in Ground Copper at D1's Cathode
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VOUT 20mV/DIV AC COUPLED VSW 5V/DIV 500ns/DIV
1614 F09
Figure 9. 33F "B" Case Tantalum Capacitor Has ESR Resulting in 40mVP-P Voltage Ripple at Output with 200mA Load
VOUT 10mV/DIV AC COUPLED
VSW 5V/DIV 500ns/DIV
1614 F11
Figure 11. 22F Ceramic Capacitor at Output Reduces Output Ripple Voltage
C1 SHUTDOWN
+
VIN
1 R1 R2 RC CC 2 3 4 D1 GND
8 7 6 5 L1
VOUT
9
LT1614
OPERATIO
Capacitors
As described previously, ceramic capacitors can be used with the LT1614. For lower cost applications, small tantalum units can be used. A value of 22F is acceptable, although larger capacitance values can be used. ESR is the most important parameter in selecting an output capacitor. The "flying" capacitor (C2 in the schematic figures) should be a 1F ceramic type. An X5R or X7R dielectric should be used to avoid capacitance decreasing severely with applied voltage. The input bypass capacitor is less
Table 1. Inductor Vendors
VENDOR Sumida Murata Coiltronics PHONE (847) 956-0666 (404) 436-1300 (407) 241-7876 URL www.sumida.com www.murata.com www.coiltronics.com PART CLS62-22022 CD43-470 LQH3C-220 CTX20-1 COMMENT 22H Coupled 47H 22H, 2mm Height 20H Coupled, Low DCR
Table 2. Capacitor Vendors
VENDOR Taiyo Yuden AVX Murata PHONE (408) 573-4150 (803) 448-9411 (404) 436-1300 URL www.t-yuden.com www.avxcorp.com www.murata.com PART Ceramic Caps Ceramic Caps Tantalum Caps Ceramic Caps COMMENT X5R Dielectric
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critical, and either tantalum or ceramic can be used with little trade-off in circuit performance. Some capacitor types appropriate for use with the LT1614 are listed in Table 2. Diodes A Schottky diode is recommended for use with the LT1614. The Motorola MBR0520 is a very good choice. Where the input to output voltage differential exceeds 20V, use the MBR0530 ( a 30V diode).
LT1614
APPLICATIONS INFORMATION
Shutdown Pin The LT1614 has a Shutdown pin (SHDN) that must be grounded to shut the device down or tied to a voltage equal or greater than VIN to operate. The shutdown circuit is shown in Figure 13. Note that allowing SHDN to float turns on both the startup current (Q2) and the shutdown current (Q3) for VIN > 2VBE. The LT1614 doesn't know what to do in this situation and behaves erratically. SHDN voltage above VIN is allowed. This merely reverse-biases Q3's base emitter junction, a benign condition. The low-battery detector is disabled when SHDN is low.
VIN Q3 R2 400k SHDN 200k START-UP CURRENT Q2 Q1
1614 F13
SHUTDOWN CURRENT
Figure 13. Shutdown Circuit
Low-Battery Detector The LT1614'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 reference. The positive input is the LBI pin. Arrangement as a low-battery detector is straightforward. Figure 14 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 15. The lowbattery detect is not operative when the device is shut down.
100k 1nF
24.9k
C1, C2: AVX TAJB336M010 C3: AVX 1206CY106 D1: MBR0520 L1: COILTRONICS CTX10-1
Figure 16. 5V to - 5V Converter with Coupled Inductor
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3.3V R1 LBI R2 100k VIN LT1614 1M LBO TO PROCESSOR
+ -
200mV INTERNAL REFERENCE GND
1614 F14
R1 =
VLB - 200mV 2A
Figure 14. Setting Low-Battery Detector Trip Point
200k 2N3906 VREF 200mV 10k LBO
VIN LT1614
+
10F
LBI GND
1614 F15
Figure 15. Accessing 200mV Reference
Coupled Inductors The applications shown in this data sheet use two uncoupled inductors because the Murata units specified are small and inexpensive. This topology can also be used with a coupled inductor as shown in Figure 16. Be sure to get the phasing right.
L1A 10H C3 1F L1B 10H
VIN 5V
*
SW 69.8k
*
+
VIN C1 33F
SHDN LT1614 VC NFB GND
VOUT - 5V 200mA D1 C2 33F
1614 F16
11
LT1614
TYPICAL APPLICATIO S
5V to - 15V/80mA DC/DC Converter
VIN 5V L1 22H C1 1F L2 22H
100k 1nF
GND
24.9k
C1: 25V, Y5V D1: MBR0520 L1, L2: MURATA LQH3C220
5V to - 15V Converter Efficiency
80 75
EFFICIENCY (%)
70 65 60 55 50 1 10 LOAD CURRENT (mA) 100
1614 TA06
12
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22F
VIN
SW 255k D1
SHDN LT1614 NFB VC
VOUT -15V 80mA 10F 25V
1614 TA05
LT1614
TYPICAL APPLICATIO S
3.3V to - 3.1V/200mA DC/DC Converter
VIN 3.3V VIN L1 22H C1 1F L2 22H
100k 1nF
GND
12.7k
C1: AVX1206CY106 D1: MBR0520 L1, L2: MURATA LQH3C220
3.3V to - 3.1V Converter Efficiency
80 70
EFFICIENCY (%)
60 50 40 30 20 3 10 30 100 LOAD CURRENT (mA) 300
1614 TA04
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SW 18.7k FB D1
+
22F
SHDN LT1614 VC
VOUT - 3.1V 200mA 22F
1614 TA03
13
LT1614
PACKAGE DESCRIPTION
0.007 (0.18) 0.021 0.006 (0.53 0.015)
0 - 6 TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.193 0.006 (4.90 0.15) 0.118 0.004** (3.00 0.102)
* 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
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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)
0.040 0.006 (1.02 0.15)
0.034 0.004 (0.86 0.102)
8
76
5
0.006 0.004 (0.15 0.102)
MSOP (MS8) 1098
1
23
4
LT1614
PACKAGE DESCRIPTION
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
0.014 - 0.019 (0.355 - 0.483) 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
0.016 - 0.050 (0.406 - 1.270)
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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Dimensions in inches (millimeters) unless otherwise noted.
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
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
15
LT1614
TYPICAL APPLICATIO S
5V to - 5V Converter Uses All Ceramic Capacitors
L1 22H C3 1F L2 22H VOUT - 5V 200mA D1 24.9k C2 10F VIN 3V TO 5V VIN C1 4.7F 100k 1nF C1: TAIYO YUDEN LMK316BJ475ML C2: TAIYO YUDEN JMK316BJ106ML C3: TAIYO YUDEN EMK316BJ105MF D1: MOTOROLA MBR0520 L1, L2: MURATA LQH3C220 OR SUMIDA CD43-220
1614 TA07
EFFICIENCY (%)
RELATED PARTS
PART NUMBER LTC(R)1174 LT1307 LT1308 LT1316 LT1317 LTC1474 LT1610 LT1611 LT1613 LT1615 LT1617 LT1930 LT1931 DESCRIPTION High Efficiency Step-Down and Inverting DC/DC Converter Single Cell Micropower 600kHz PWM DC/DC Converter Single Cell High Current Micropower 600kHz Boost Converter Micropower Boost DC/DC Converter Micropower 600kHz PWM DC/DC Converter Low Quiescent Current High Efficiency DC/DC Converter 1.7MHz Single Cell Micropower DC/DC Converter Inverting 1.4MHz Switching Regulator in 5-Lead SOT-23 1.4MHz Switching Regulator in 5-Lead SOT-23 Micropower Constant Off-Time DC/DC Converter in 5-Lead SOT-23 Micropower Inverting DC/DC Converter in 5-Lead SOT-23 1.2MHz Boost DC/DC Converter in 5-Lead SOT-23 1.2MHz Inverting DC/DC Converter in 5-Lead SOT-23 COMMENTS Selectable IPEAK = 300mA or 600mA 3.3V at 75mA from 1 Cell, MSOP Package 5V at 1A from a Single Li-Ion Cell, SO-8 Package Programmable Peak Current Limit, MSOP Package 2 Cells to 3.3V at 200mA, MSOP Package IQ = 10A, Programmable Peak Current Limit, MSOP 5V at 200mA from 3.3V, MSOP Package - 5V at 150mA from 5V Input, Tiny SOT-23 Package 5V at 200mA from 3.3V Input, Tiny SOT-23 Package 20V at 12mA from 2.5V, Tiny SOT-23 Package -15V at 12mA from 2.5V, Tiny SOT-23 Package 5V at 480mA from 3.3V Input, VOUT Up to 34V -5V at 350mA from 5V Input, 1mVP-P Output Ripple
sn1614 1614fs LT/TP 1000 4K * PRINTED IN THE USA
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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SW 1nF 69.8k
SHDN LT1614 VC NFB GND
Efficiency vs Load Current
80 75 70 65 60 55 50 45 40 1
VIN = 3V VOUT = -5V
10 LOAD CURRENT (mA)
100
1614 TA08
(c) LINEAR TECHNOLOGY CORPORATION 1998

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