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LTC1516 Micropower, Regulated 5V Charge Pump DC/DC Converter
FEATURES
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DESCRIPTION
The LTC(R)1516 is a micropower charge pump DC/DC converter that produces a regulated 5V output from a 2V to 5V supply. Extremely low supply current (12A typical with no load, < 1A in shutdown) and low external parts count (two 0.22F flying capacitors and two 10F capacitors at VIN and VOUT) make the LTC1516 ideally suited for small, light load battery-powered applications. Typical efficiency (VIN = 3V) exceeds 70% with load currents between 50A and 50mA. Modulating the SHDN pin keeps the typical efficiency above 70% with load currents all the way down to 10A. The LTC1516 operates as either a doubler or a tripler depending on VIN and output load conditions to improve overall efficiency. The part has thermal shutdown and can survive a continuous short from VOUT to GND. In shutdown the load is disconnected from VIN. The LTC1516 is available in an 8-pin SO package in both commercial and industrial temperature grades.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Ultralow Power: Typical Operating ICC = 12A Short Circuit/Thermal Protection Regulated 5V 4% Output 2V to 5V Input Range No Inductors ICC in Shutdown: < 1A Output Current: 20mA (VIN > 2V) 50mA (VIN > 3V) Shutdown Disconnects Load from VIN Internal Oscillator: 600kHz Compact Application Circuit (0.1 in2) 8-Pin SO Package
APPLICATIONS
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2-Cell to 5V Conversion Li-Ion Battery Backup Supplies Local 3V to 5V Conversion 5V Flash Memory Programmer Smart Card Readers
TYPICAL APPLICATION
0.22F
Efficiency vs Output Current
90 VIN = 3V
1 2
C1+ VIN VOUT C2+ 0.22F
8 C1-
80
+
10F 3 10F 4
EFFICIENCY (%)
VIN = 2V TO 5V
SHDN LTC1516 GND C2 -
7 6 5
ON/OFF
70
+
SHDN = 0V 60
VOUT = 5V 4% IOUT = 0mA TO 20mA, VIN 2V IOUT = 0mA TO 50mA, VIN 3V
50 0.01
1516 * F01
Figure 1. Regulated 5V Output from a 2V to 5V Input
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LOW IQ MODE (SEE FIGURE 3)
0.1 1 10 OUTPUT CURRENT (mA)
100
1516 * TA01
1
LTC1516
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW C1+ 1 VIN 2 VOUT 3 C2+ 4 8 C1- 7 SHDN 6 GND 5 C2-
VIN to GND ...................................................- 0.3V to 6V VOUT to GND ................................................- 0.3V to 6V SHDN to GND ..............................................- 0.3V to 6V VOUT Short-Circuit Duration ............................. Indefinite Operating Temperature Range Commercial ............................................. 0C to 70C Industrial ............................................ - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC1516CS8 LTC1516IS8 S8 PART MARKING 1516 1516I
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 125C, JA = 150C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER VIN Input Voltage VOUT Output Voltage CONDITIONS
VIN = 2V to 5V, C1 = C2 = 0.22F, CIN = COUT = 10F, TMIN to TMAX unless otherwise specified (Note 3).
q
ICC
Supply Current Output Ripple Efficiency Switching Frequency SHDN Input Threshold SHDN Input Current VOUT Turn-On Time
fOSC VIH VIL IIH IIL tON
2V VIN 5V, IOUT 20mA 3V VIN 3.6V, IOUT 50mA 3.6V VIN 5V, IOUT 50mA, TA = 25C (Note 2) 2V VIN 5V, IOUT = 0mA, SHDN = 0V 2V VIN 5V, IOUT = 0mA, SHDN = VIN Full Load VIN = 3V, IOUT = 20mA Full Load
q q q q
MIN 2 4.8 4.8 4.8
TYP
12 0.005 100 82 600 (0.7)(VIN) -1 -1 500
MAX 5 5.2 5.2 5.2 20 1
q q
VSHDN = VIN VSHDN = 0V VIN = 3V, IOUT = 0mA (Note 3)
q q
0.4 1 1
UNITS V V V V A A mV % kHz V V A A s
The q denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired
Note 2: At input voltages > 3.6V and ambient temperatures >70C, continuous power dissipation must be derated to maintain junction temperatures below 125C. Derate 6mW/C above 70C in SO-8. Note 3: The LTC1516 is tested with the capacitors shown in Figure 1.
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LTC1516 TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Input Voltage
90 IOUT = 10mA
MAXIMUM OUTPUT CURRENT (mA)
EFFICIENCY (%)
80 60 40 20 0
C1 = C2 = 0.1F C1 = C2 = 0.047F C1 = C2 = 0.022F C1 = C2 = 0.01F
SUPPLY CURRENT (A)
80
70
60
50 2.0 2.5 3.0 3.5 4.0 INPUT VOLTAGE (V) 4.5 5.0
Output Voltage vs Input Voltage
5.10 IOUT = 20mA 5.05
5.05 5.10
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.00
4.95
4.90 1 2 3 4 INPUT VOLTAGE (V) 5 6
1516 * G04
PIN FUNCTIONS
C1+ (Pin 1): Flying Capacitor 1, Positive Terminal. VIN (Pin 2): Input Supply Voltage. VOUT (Pin 3): 5V Output Voltage (VOUT = 0V in Shutdown). C2+ (Pin 4): Flying Capacitor 2, Positive Terminal. C2 - (Pin 5): Flying Capacitor 2, Negative Terminal. GND (Pin 6): Ground. SHDN (Pin 7): Active High CMOS Logic-Level Shutdown Input. C1 - (Pin 8): Flying Capacitor 1, Negative Terminal.
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1516 * G01
Output Current vs Input Voltage
120 COUT = 10F TA = 25C 100 C1 = C2 = 0.22F
No Load Supply Current vs Input Voltage
20
15
10
5
5
2
3 4 INPUT VOLTAGE (V)
2
3 4 INPUT VOLTAGE (V)
5
1516 * G03
1516 * G02
Output Voltage vs Output Current
VIN = 3V
Load Transient Response, VIN = 3V
IOUT , 0mA TO 25mA, 10mA/DIV
5.00
VOUT, AC COUPLED, 100mV/DIV
4.95
1516 * G04
4.90 0.01 0.1 1 10 OUTPUT CURRENT (mA) 100
1516 * G05
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LTC1516
BLOCK DIAGRAM
VIN 10F
+
S2A S1A S2B C2 - COMP1 S1B CLOCK 1 COMP2 C1 + S1C S2C C1 - S1D S3 VREF CHARGE PUMP CLOCK 2 COMP3 VOS CONTROL LOGIC
C2 + 0.22F
0.22F
CHARGE PUMP SHOWN IN TRIPLER MODE, DISCHARGE CYCLE
APPLICATIONS INFORMATION
Operation The LTC1516 uses a switched capacitor charge pump to boost VIN from 2V to 5V to a regulated 5V 4% output voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and enabling the charge pump when the output voltage droops below the lower trip point of COMP2. When the charge pump is enabled, a 2-phase, nonoverlapping clock controls the charge pump switches. Clock 1 closes the S1 switches which enable the flying capacitors, C1 and C2, to charge up to the VIN voltage. Clock 2 closes the S2 switches which stack C1 and C2 in series with VIN and connect the top plate of C2 to the output capacitor at VOUT. This sequence of charging and discharging continues at a free-running frequency of 600kHz (typ) until the output has risen to the upper trip point of COMP2 and the charge pump is disabled. When the charge pump is disabled, the LTC1516 draws only 8A (typ) from VIN which provides high efficiency at low load conditions. To achieve the highest efficiency over the entire VIN range, the LTC1516 operates as either a doubler or a tripler depending on VIN and output load conditions. COMP1 and COMP2 determine whether the charge pump is in doubler mode or tripler mode. COMP1 forces the part into tripler mode if VIN is < 2.55V, regardless of output load. When VIN is > 2.55V, the part will be in doubler mode using only C2 as a flying capacitor. In doubler mode, if the output droops by 50mV under heavy loads, COMP3 will force the charge pump into tripler mode until VOUT climbs above the upper trip point of COMP3. Under these VIN and load conditions, the nominal VOUT will be approximately 50mV lower than the no load nominal VOUT. This method of sensing VIN and output load results in efficiency greater than 80% with VIN between 2.5V and 3V. In shutdown mode, all circuitry is turned off and the part draws only leakage current (< 1A) from the VIN supply. VOUT is also disconnected from VIN. The SHDN pin is a CMOS input with a threshold of approximately VIN/2; however, the SHDN pin can be driven by logic levels that exceed the VIN voltage. The part enters shutdown mode when a logic high is applied to the SHDN pin. The SHDN pin cannot float; it must be driven with a logic high or low.
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SHDN VOUT
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10F
LTC1516 * BD
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LTC1516
APPLICATIONS INFORMATION
Short-Circuit/Thermal Protection During short-circuit conditions, the LTC1516 will draw between 200mA and 400mA from VIN causing a rise in the junction temperature. On-chip thermal shutdown circuitry disables the charge pump once the junction temperature exceeds 135C, and reenables the charge pump once the junction temperature falls back to 115C. The LTC1516 will cycle in and out of thermal shutdown indefinitely without latchup or damage until the VOUT short is removed. Capacitor Selection For best performance, it is recommended that low ESR capacitors be used for both CIN and COUT to reduce noise and ripple. The CIN and COUT capacitors should be either ceramic or tantalum and should be 10F or greater. If the input source impedance is very low, CIN may not be needed. Increasing the size of COUT to 22F or greater will reduce output voltage ripple. Ceramic or tantalum capacitors are recommended for the flying caps C1 and C2 with values in the range of 0.1F to 1F. Note that large value flying caps (> 0.22F) will increase output ripple unless COUT is also increased. For very low load applications, C1 and C2 may be reduced to 0.01F to 0.047F. This will reduce output ripple at the expense of efficiency and maximum output current. Output Ripple Normal LTC1516 operation produces voltage ripple on the VOUT pin. Output voltage ripple is required for the LTC1516 to regulate. Low frequency ripple exists due to the hysteresis in the sense comparator and propagation delays in the charge pump enable/disable circuits. High frequency ripple is also present mainly due to ESR (Equivalent Series Resistance) in the output capacitor. Typical output ripple under maximum load is 100mVP-P with a low ESR 10F output capacitor. The magnitude of the ripple voltage depends on several factors. High input voltages (VIN > 3.3V) increase the output ripple since more charge is delivered to COUT per clock cycle. Large C1 and C2 flying capacitors (> 0.22F) also increase ripple for the same reason. Large output current load and/or a small output capacitor (< 10F) results in
LTC1516 3 VOUT
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higher ripple due to higher output voltage dV/dt. High ESR capacitors (ESR > 0.5) on the output pin cause high frequency voltage spikes on VOUT with every clock cycle. There are several ways to reduce the output voltage ripple. A larger COUT capacitor (22F or greater) will reduce both the low and high frequency ripple due to the lower COUT charging and discharging dV/dt and the lower ESR typically found with higher value (larger case size) capacitors. A low ESR ceramic output capacitor will minimize the high frequency ripple, but will not reduce the low frequency ripple unless a high capacitance value is chosen. A reasonable compromise is to use a 10F to 22F tantalum capacitor in parallel with a 1F to 3.3F ceramic capacitor on VOUT to reduce both the low and high frequency ripple. An RC filter may also be used to reduce high frequency voltage spikes (see Figure 2). In low load or high VIN applications, smaller values for C1 and C2 may be used to reduce output ripple. The smaller C1 and C2 flying capacitors (0.022F to 0.1F) deliver less charge per clock cycle to the output capacitor resulting in lower output ripple. However, the smaller value flying caps also reduce the maximum IOUT capability as well as efficiency.
LTC1516 3 VOUT
+
15F TANTALUM
1F CERAMIC
VOUT 5V
2
+
10F
+
10F
VOUT 5V
1516 F02
Figure 2. Output Ripple Reduction Techniques
Inrush Currents During normal operation, VIN will experience current transients in the 100mA to 200mA range whenever the charge pump is enabled. During start-up, these inrush currents may approach 500mA. For this reason, it is important to minimize the source resistance between the input supply and the VIN pin to prevent start-up problems and large input voltage transients.
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LTC1516
APPLICATIONS INFORMATION
Ultralow Quiescent Current (IQ < 5A) Regulated Supply The LTC1516 contains an internal resistor divider (refer to Block Diagram) which draws only 1.5A (typ) from VOUT. During no-load conditions, the internal load causes a droop rate of only 150mV per second on VOUT with COUT = 10F. Applying a 5Hz to 100Hz, 95% to 98% duty cycle signal to the SHDN pin ensures that the circuit of Figure 3 comes out of shutdown frequently enough to maintain regulation during no-load or low-load conditions. Since the part spends nearly all of its time in shutdown, the no-load quiescent current (see Figure 4a) is approximately equal to (VOUT)(1.5A)/(VIN)(Efficiency).
0.22F
1 2
C1+ VIN VOUT C2+ 0.22F
C1- SHDN LTC1516 GND C2 -
8 7 6 5
VIN = 2V TO 5V
+
10F 3 10F 4
+
VOUT = 5V 4%
Figure 3. Ultralow Quiescent Current (<5A) Regulated Supply
6.0
4.0
MAXIMUM SHDN OFF TIME (ms)
SUPPLY CURRENT (A)
2.0
0.0 2.0
3.0 4.0 INPUT VOLTAGE (V)
5.0
1516 * F04a
Figure 4a. No Load ICC vs Input Voltage for Circuit in Figure 3
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The LTC1516 must be out of shutdown for a minimum duration of 200s to allow enough time to sense the output and keep it in regulation. As the VOUT load current increases, the frequency with which the part is taken out of shutdown must also be increased to prevent VOUT from drooping below 4.8V during the OFF phase (see Figure 4b). A 100Hz 98% duty cycle signal on the SHDN pin ensures proper regulation with load currents as high as 100A. When load current greater than 100A is needed, the SHDN pin must be forced low as in normal operation. The typical no-load supply current for this circuit with VIN = 3V is only 3.2A.
FROM MPU
SHDN PIN WAVEFORMS:
LOW IQ MODE (5Hz TO 100Hz, 95% TO 98% DUTY CYCLE) VOUT LOAD ENABLE MODE IOUT 100A (IOUT = 100A TO 50mA)
1516 * F03
1000 SHDN ON PULSE WIDTH = 200s COUT = 10F
100
10
1 1 10 100 OUTPUT CURRENT (A) 1000
1516 * F04b
Figure 4b. Maximum SHDN OFF Time vs Output Load Current for Ultralow IQ Operation
LTC1516
APPLICATIONS INFORMATION
Paralleling Devices Two or more LTC1516's may be connected in parallel to provide higher output currents. The VIN, VOUT, GND and SHDN pins may be tied together, but the C1 and C2 pins must be kept separate (see Figure 5). Separate CIN and COUT capacitors may be required to reduce output noise and ripple if the paralleled devices cannot be kept close together. Otherwise, single CIN and COUT capacitors may be used with each being 2x (or 3x if three parts are paralleled, etc.) in value.
0.22F
1 2 3 4
C1+ VIN VOUT C2+ 0.22F
C1- SHDN LTC1516 GND C2 -
8 7 6 5
VIN
VOUT COUT
0.22F
Figure 6. Suggested Component Placement for LTC1516
1 VIN = 2V TO 5V 2
C1+ VIN VOUT C2+ 0.22F
C1- SHDN LTC1516 GND C2 -
8 7 6 5
+
22F 3
ON/OFF
+
22F 4
VOUT = 5V 4% IOUT = 0mA TO 40mA, VIN 2V IOUT = 0mA TO 100mA, VIN 3V
1516 * F05
Figure 5. Paralleling Devices
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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General Layout Considerations Due to the high switching frequency and high transient currents produced by the LTC1516, careful board layout is a must. A clean board layout using a ground plane and short connections to all capacitors will improve performance and ensure proper regulation under all conditions (refer to Figure 6).
C1
CIN
1 2 LTC1516 3
8 7 6 GND 5 SHDN
+
4
C2
1516 * F06
7
LTC1516
TYPICAL APPLICATIONS N
Fault-Protected SIM Interface Supply for GSM Cellular Phones
0.1F 3V 1 C1+ C1- 8 3 6 5
10F 1 C1+ C1- 8 3 240 6 5 0.22F 2.2F Q1 Q2 3.3k ** * 10F - VOUT = -1.4V TO - 3V - IOUT = 5mA 8.2k
2V IN
+
VOUT LTC1516 7 SHDN GND 10F 4 C2+ 0.1F C2 -
GSM CONTROLLER VCC RST LEVEL SHIFT CLK I/O GND
1516 * TA02
SIM CARD
*CENTRAL SEMICONDUCTOR CMPSH-35 DUAL SCHOTTKY **OPTIONAL CIRCUITRY FOR MAINTAINING - VOUT AT LOW VOUT LOADS Q1, Q2: 2N3904
PACKAGE DESCRIPTION
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) 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0.053 - 0.069 (1.346 - 1.752) 0- 8 TYP 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157** (3.810 - 3.988) 0.004 - 0.010 (0.101 - 0.254) 8 7 6 5
0.016 - 0.050 0.406 - 1.270
0.014 - 0.019 (0.355 - 0.483)
*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
0.050 (1.270) BSC
SO8 0695
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RELATED PARTS
PART NUMBER LT 1054 LTC1144 LTC1261 LTC1262 LTC1550/51
(R)
DESCRIPTION 100mA Switched Capacitor Converter 20mA Switched Capacitor Converter for Up to 20V Inputs Positive to Negative Regulated Switched Capacitor Converter 5V to 12V Regulated Switched Capacitor Converter Low Noise Switched Capacitor Regulated Converter
COMMENTS Includes Reference and Amplifier for Regulation Includes Micropower Shutdown (8A) Low Noise (5mV) Output for Up to 10mA Loads Up to 30mA at Regulated Output Provides - 4.1V at 20mA with <1mV Ripple
LT/GP 0796 7K * PRINTED IN USA
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
(c) LINEAR TECHNOLOGY CORPORATION 1996
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Generating 5V and a Negative Supply
0.1F VOUT = 5V 4% IOUT = 20mA,VIN 2V IOUT = 50mA, VIN 3V
10F
VOUT = 5V 4% IOUT = 40mA
ON/OFF VIN 2V TO 5V
7
+
SHDN VOUT LTC1516 2 VIN GND 4 C2+ 0.1F C2 -
1516 * TA03

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