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ILC6390/91
SOT-89 Step-Up PFM Switcher with Auto-Load Sense
Features
85% conversion efficiency at 50mA out Start-up voltages as low as 900mV 2.5% accurate outputs Complete switch design with only 3 external components Automatically senses load variations to select the optimal duty cycle and extend conversion efficiency over a wide range * External transistor configuration to run as switcher controller * Shutdown to 0.5A * * * * *
Description
50 mA boost converter using Pulse Frequency Modulation, or PFM, technique, in 5-lead SOT-89 or a 5-lead SOT-23 package. Only 3 external components are needed to complete the switcher design. The ILC6390 automatically senses load variations to choose between 55% and 75% duty cycles. Normal operation is 55% duty at 155kHz; when load currents exceed the internal comparator trip point, a "turbo mode" kicks in to provide extended on-time switching (75% duty at 100kHz oscillation). Requiring only 30A of supply current, the ILC6390 achieves efficiencies as high as 85% at 5V yet shuts down to 0.5A max. Standard voltages offered are 2.5, 3.3, and 5.0V and is available in both a 5 lead SOT-23 and 5 lead SOT-89 package for small footprint applications. In addition, the ILC6391 is configured to drive an external transistor to achieve higher power levels.
Applications
* Cellular phones, pagers * Cameras, video recorders * Palmtops and PDAs
Typical Applications
Figures 1 & 2
SD
3 1
CE V
3 2 1
OUT
L: 100H (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA 735)
L + V IN
4
L V IN
1
ILC6390CM
2 3
ILC6390CP
5
CL
+
V OUT CL
CL: 16V 47F (Tantalum Capacitor; NICHICON, f93)
SD CE GND
GND
SD
3 2 1
CE V
OUT
Figures 3 & 4
L: 47H (SUMIDA, CD-54) SD: Diode (Schottky diode; MATSUSHITA MA735) CL: 16V 47F (Tantalum Capacitor; NICHICON, F93) RB: 1k CB: 3300pF Tr: 2SC3279, 2SDI628G Rev.1.2
(c)2001 Fairchild Semiconductor Corporation
SD
3 2 1
CE V
OUT
L + V IN
4
L V IN CB
ILC6391CM
5
CL
+
ILC6391CP
4 5
CL
Tr R GND
Tr RB GND
ILC6390/91
Pin Assignments
LX 5 V SS 4 LX 5 V SS 4
SOT-25
(TOP VIEW)
1 CE 2 V DD 3 N/C 1 CE
SOT-25
(TOP VIEW)
2 VDD 3 N/C
ILC6390CM
V SS 5 LX 4 V SS 5
ILC6391CM
LX 4
SOT-89-5
(TOP VIEW)
1 N/C 2 VOUT 3 CE 1 N/C
SOT-89-5
(TOP VIEW)
2 V OUT 3 CE
ILC6390CP
ILC6391CP
Internal Block Diagram
LX
VLX LIMITER BUFFER VREF
V DD V OUT
V SS EXT
2-STEP PFM CONTROLLED OSC 100/155kHz
+ +
CE
CHIP ENABLE
-
4~5mV
Absolute Maximum Ratings (
Parameter VOUT Input Voltage Voltage on pin LX Current on pin LX Voltage on pin EXT Current on pin EXT CE Input Voltage VDD Input Voltage Continuous Total Power Dissipation Operating Ambient Temperature Storage Temperature
A
= 25C)
Symbol VOUT VLX ILX VEXT IEXT VCE VDD PD (SOT-25) PD(SOT-89) Topr Tstg Ratings 12 12 400 VSS-0.3~VOUT +0.3 50 12 12 150 500 -30~+80 -40~+125 Units V V mA V mA V V mW C C
(c)2001 Fairchild Semiconductor Corporation
2
ILC6390/91
Electrical Characteristics ILC6390
VOUT = 5.0V TA = 25C. Unless otherwise specified, VIN = VOUT x 0.6, IOUT = 50mA. See schematic, fig. 1 & 2. Parameter Output Voltage Input Voltage Oscillation Startup Voltage Oscillation Hold Voltage NO-Load Input Current Supply Current 1 (Note 2) Supply Current 2 LX Switch-On Resistance LX Leakage Current Duty Ratio 1 Duty Ratio 2 Maximum Oscillation Freq. 1 Maximum Oscillation Freq. 2 Stand = by Current CE "High" Voltage CE "Low" Voltage CE "High" Current CE "Low" Current LX Limit Voltage Efficiency
Note: 1. The Schottky diode (S.D.), in figure 3 must be type MA735, with Reverse current (IR) < 1.0A at reverse voltage (VR)=10.0V 2. "Supply Current 1" is the supply current while the oscillator is continuously oscillating. In actual operation the oscillator periodically operates which results in less average power consumption. The current that is actually provided by external V IN source is represented by "No-Load Input Current." 3. The switching frequency is determined by the delay time of the internal comparator and MFO1, which sets the min. on-time
Symbol VOUT VIN VST VHLD IIN IDD1 RSWON ILXL DUTY 1 DUTY 2 MFO 1 MFO 2 ISTB VCEH VCEL ICEH ICEL VLXLMT EFFI
Conditions Test Circuit Figures 1 & 2 IOUT = 1mA IOUT = 1mA IOUT = 0mA (Note1) VOUT = 4.75V VOUT = 5.5V VOUT = 4.75V, VLX = 0.4 No external components, VOUT = VLX = 10V VOUT = 4.75V, Measuring of LX waveform VOUT = 4.75V, Measuring of LX ontime VOUT = 4.75V, 75% duty VOUT = 4.75V, 55% duty VOUT = 4.75V VOUT = 4.75V, Existence of LX Oscillation VOUT = 4.75V, Disappearance of LX Oscillation VCE = VOUT x 0.95 VOUT = 4.75V, VCE = 0V VOUT = 4.75V, fOSC > MFO x 2 (Note 3) Test Circuit Figures 1 & 2
Min. 4.875
Typ. 5.000 0.80
Max. 5.125 10 0.9 10.6 63.4 4.8 4.3 1.0 80 60 115 207 0.5
0.70 5.3 31.7 2.4 2.8
Units V V V V A A A A % % kHz kHz A V V A A V %
70 50 85 153 0.75
75 55 100 180
0.20 0.25 -0.25 1.1 85
0.7
(c)2001 Fairchild Semiconductor Corporation
3
ILC6390/91
Electrical Characteristics ILC6390
VOUT = 5.0V TA = 25C. Unless otherwise specified, VIN = VOUT x 0.6, IOUT = 50mA. See schematic, fig. 3 & 4. Parameter Output Voltage Input Voltage Operation Startup Voltage Operation Hold Voltage Supply Current 1 (Note 1) Supply Current 2 EXT "High" On-Resistance EXT "Low" On-Resistance Duty Ratio 1 Duty Ratio Maximum Oscillation Freq. 1 Maximum Oscillation Freq. 2 Stand = by Current CE "High" Voltage CE "Low" Voltage CE "High" Current CE "Low" Current Efficiency Note: 1. "Supply Current 1" is the supply current while the oscillator is continuously oscillating. In actual operation the oscillator periodically operates which results in less average power consumption. EFFI Symbol VOUT VIN VST VST IDD 1 IDD 2 REXTH REXTL DUTY 1 DUTY 2 MFO 1 MFO 2 ISTB VCEH ICEL ICEH IOUT = 1mA IOUT = 1mA VOUT = 4.75V VOUT = 5.5V VOUT = 4.75V, VEXT = VOUT-0.4 VOUT = 4.75V, VEXT = 0.4 VOUT = 4.75V, Measuring of EXT waveform VIN = VOUT x 0.95, IOUT = 1mA, Measuring of EXT High State VOUT = 4.75V, 75% duty VIN = VOUT x 0.95, 55% duty VOUT = 4.75V VOUT = 4.75V, Existence of EXT Oscillation VOUT = 4.75V, Disappearance of EXT Oscillation VCE = VOUT = 4.75V VOUT = 4.75, VCE = 0V Test Circuit Figures 3 & 4 85 0.75 0.20 0.25 -0.25 70 50 85 153 0.70 31.7 2.4 50 50 75 55 100 180 63.4 4.8 75 75 80 60 115 207 0.5 0.80 Conditions Test Circuit Figures 3 & 4 Min. 4.875 Typ. 5.000 Max. 5.125 10 0.9 Units. V V V V A A % % kHz kHz A V V A A %
(c)2001 Fairchild Semiconductor Corporation
4
ILC6390/91
The ILC6390 performs boost DC-DC conversion by controlling the switch element shown in the circuit below.
The chief advantage of using a PFM technique is that, at low currents, the switcher is able to maintain regulation without constantly driving a switch on and off. This power savings can be 5mA or more for the ILC6390 versus the ILC6370, and at very light loads this current difference can make a noticeable impact on overall efficiency. However, because the ILC6390 will skip pulses based on load current, the effective frequency of switching may well drop into the audio band. This means that the radiated noise of the ILC6390 may interfere with the audio channel of the system and additional filtering may be necessary. In addition, because the PFM on-time is fixed, it usually has higher output ripple voltage than the PWM switcher, which dynamically changes the on-time to match the load current requirements. [Ripple is due to the output cap constantly accepting and storing the charge received from the inductor, and delivering charge as required by the load. The "pumping" action of the switch produces a sawtooth-shaped voltage as seen by the output.] On the plus side, because pulses are skipped, overtone content of the frequency noise is lower than in a PWM configuration. The sum of these characteristics for PFM converters makes it the ideal choice for low-current or ultra-long runtime applications, where overall conversion efficiency at low currents is of primary concern. [For other conversion techniques, please see the ILC6370/71 and ILC6380/81 datasheets.]
When the switch is closed, current is built up through the inductor. When the switch opens, this current has to go somewhere and is forced through the diode to the output. As this on and off switching continues, the output capacitor voltage builds up due to the charge it is storing from the inductor current. In this way, the output voltage gets boosted relative to the input. The ILC6390 monitors the voltage on the output capacitor to determine how much and how often to drive the switch. In general, the switching characteristic is determined by the output voltage desired and the current required by the load. Specifically the energy transfer is determined by the power stored in the coil during each switching cycle. PL = (tON, VIN) The ILC6390 and ILC6391 use a PFM or Pulse Frequency Modulation technique. In this technique, the switch is always turned on for a fixed period of time, corresponding to a fixed switching frequency at a predefined duty cycle. For the ILC6390 this value is 3.55msec on time, corresponding to 55% duty cycle at 155kHz. Because the inductor value, capacitor size, and switch on-time and frequency are all fixed, the ILC6390 in essence delivers the same amount of power to the output during each switching cycle. This in turn creates a constant output voltage ramp which is dependent on the output load requirement. In this mode, the only difference between the PFM and PWM techniques is the duty cycle of the switch. Once the output voltage reaches the set point, the ILC6390 will shut off the switch oscillator and wait until the output voltage drops low again, at which point it will re-start the oscillator. As you can see in the diagram, the PFM boost converter actually skips pulses as a way of varying the amount of power being delivered to the output.
Switch Waveform
Dual-Step Mode
The ILC6390 and ILC6391 have one other unique feature, that being to automatically switch to a second switching scheme in the presence of heavy output loading. As we mentioned, the standard switching scheme for these parts is a 3.55msec, 155kHz, 55% duty cycle part. However, if the device detects that the output load increases beyond a set point (as seen by the voltage drop on the output capacitor), it switches in a 7.5msec, 100kHz, 75% duty cycle "turbo mode" specifically to keep up with the increased load demand. This switchover is seamless to the user, but will result in a change in the output ripple voltage characteristic of the DC-DC converter. PFM converters are widely used in portable consumer applications not requiring a high current level and relatively unaffected by audio noise. Applications such as pagers and PDAs, which need to operate in stand-by for extended periods of time, gravitate toward the advantages of PFM since maximum run-time is a chief differentiating element. The ILC6390 addresses this low-current requirement, and additionally offers a "turbo" mode which maintains output regulation in the presence of heavier-than-normal load currents, and maintains 0.5mA shutdown currents. The only difference between the ILC6390 and ILC6391 parts is that the 6391 is configured to drive an external transistor as the switch element. Since larger transistors can be selected for this element, higher effective loads can be regulated.
V SET
V OUT
Because of this, PFM is sometimes called "Pulse Skipping Modulation."
(c)2001 Fairchild Semiconductor Corporation
5
ILC6390/91
External Components and Layout Consideration
The ILC6390 is designed to provide a complete DC-DC converter solution with a minimum of external components. Ideally, only three externals are required: the inductor, a pass diode, and an output capacitor. The inductor needs to be of low DC Resistance type, typically 1 value. Toroidal wound inductors have better field containment (less high frequency noise radiated out) but tend to be more expensive. Some manufacturers like Coilcraft have new bobbin-wound inductors with shielding included, which may be an ideal fit for these applications. Contact the manufacturer for more information. The inductor size needs to be in the range of 47mH to 1mH. In general, larger inductor sizes deliver less current, so the load current will determine the inductor size used. For load currents higher than 10mA, use an inductor from 47mH to 100mH. [The 100mH inductor shown in the datasheet is the most typical used for this application.] For load currents of around 5mA, such as pagers, use an inductor in the range of 100mH to 330mH. 220mH is the most typical value used here. For lighter loads, an inductor of up to 1mH can be used. The use of a larger inductor will increase overall conversion efficiency, due to the reduction in switching currents through the device. For the ILC6391, using an external transistor, the use of a 47mH inductor is recommended based on our experience with the part. The capacitor should, in general, always be tantalum type, as tantalum has much better ESR and temperature stability than other capacitor types. NEVER use electrolytics or chemical caps, as the C-value changes below 0xC so much as to make the overall design unstable. Different C-values will directly impact the ripple seen on the output at a given load current, due to the direct charge-tovoltage relationship of this element. Different C-values will also indirectly affect system reliability, as the lifetime of the capacitor can be degraded by constant high current influx and outflux. Running a capacitor near its maximum rated voltage can deteriorate lifetime as well; this is especially true for tantalum caps which are particularly sensitive to overvoltage conditions. In general, then, this capacitor should always be 47mF, Tantalum, 16V rating. The diode must be of shottkey type for fast recovery and minimal loss. A diode rated at greater than 200mA and maximum voltage greater than 30V is recommended for the fastest switching time and best reliability over time. Different diodes may introduce different levels of high frequency switching noise into the output waveform, so trying out several sources may make the most sense for your system.
For the IL6391, much of the component selection is as described above, with the addition of the external NPN transistor and the base drive network. The transistor needs to be of NPN type, and should be rated for currents of 2A or more. [This translates to lower effective on resistance and, therefore, higher overall efficiencies.] The base components should remain at 1k and 3300pF; any changes need to be verified prior to implementation. As for actual physical component layout, in general, the more compact the layout is, the better the overall performance will be. It is important to remember that everything in the circuit depends on a common and solid ground reference. Ground bounce can directly affect the output regulation and presents difficult behavior to predict. Keeping all ground traces wide will eliminate ground bounce problems. It is also critical that the ground pin of C L and the VSS pin of the device be the same point on the board, as this capacitor serves two functions: that of the output load capacitor, and that of the input supply bypass capacitor. Layouts for DC-DC converter designs are critical for overall performance, but following these simple guidelines can simplify the task by avoiding some of the more common mistakes made in these cases. Once actual performance is completed, though, be sure to double-check the design on actual manufacturing prototype product to verify that nothing has changed which can affect the performance.
(c)2001 Fairchild Semiconductor Corporation
6
ILC6390/91
Typical Performance Characteristics General conditions for all curves
Output Voltage vs Output Current
ILC6390CP-30
L = 100H C = 10F (Tantalum)
Efficiency vs. Output Current
100
ILC6391CP-30
4.0 3.5
80 EFFICIENCY: EFFI (%)
VIN = 1.8V
OUTPUT VOLTAGE: VOUT(V)
3.0
VIN = 2.0V
60
VIN = 1.0V
VIN = 1.2V VIN = 1.5V
2.5
VIN = 1.2V
VIN = 1.5V VIN = 1.8V
40
L = 22H (CD105) RB = 300 CB = 0
2.0
VIN = 0.9V
1.5 1.0 0.5 0 20 40 60 80 100 OUTPUT CURRENT I OUT (mA)
20
0 0 100 200 300 400 500 OUTPUT CURRENT I OUT (mA)
Output Voltage vs. Output Current
ILC6390CP-50
L = 100H C = 10F (Tantalum)
Efficiency vs. Output Current
7.0 100
ILC6390CP-30
OUTPUT VOLTAGE: VOUT(V)
L = 100H C = 10F (Tantalum)
6.0 5.0 4.0 3.0
VIN = 1.5V
80 EFFICIENCY: EFFI (%)
VIN = 3.0V
60
VIN = 0.9V VIN = 1.2V VIN = 1.5V VIN = 1.8V VIN = 2.0V
40
VIN = 2.0V
2.0
VIN = 0.9V
VIN = 1.2V
20
1.0 0 0 20 40 60 80 100 OUTPUT CURRENT I OUT (mA) 0 0 20 40 60 80 100
OUTPUT CURRENT I OUT (mA)
Ripple Voltage vs. Output Current
100
Efficiency vs. Output Current
100
ILC6390CP-30
L = 100H C = 10F (Tantalum)
ILC6390CP-50
80 EFFICIENCY: EFFI (%) RIPPLE Vr (mV p-p)
80
VIN = 3.0V
60
VIN = 1.5V
60
VIN = 0.9V
VIN = 1.2V V = 1.5V IN VIN = 2.0V
40
VIN = 1.2V
40
20
VIN = 0.9V
20
L = 100H C = 10F (Tantalum)
0 0 20 40 60 80 100 OUTPUT CURRENT I OUT (mA)
0 0 20 40 60 80 100 OUTPUT CURRENT I OUT (mA)
(c)2001 Fairchild Semiconductor Corporation
7
ILC6390/91
Typical Performance Characteristics General conditions for all curves
Ripple Voltage vs. Output Current
100
Output Voltage vs. Output Current
ILC6391CP-30
ILC6390CP-50
4.0
L = 100H C = 10F (Tantalum) VIN = 3.0V
80 RIPPLE Vr (mV p-p) OUTPUT VOLTAGE: VOUT(V)
3.5 3.0 2.5
VIN = 1.0V VIN = 1.2V VIN = 1.8V VIN = 1.5V
60
VIN = 2.0V VIN = 1.5V
40
2.0 1.5 1.0
L = 22H (CD105) RB = 300 CB = 0
20
0 0 20 40 60 80 100 OUTPUT CURRENT I OUT (mA)
0.5 0
20
40
60
80
100
Efficiency vs. Output Current
100
OUTPUT CURRENT I OUT (mA)
ILC6391CP-50
Output Voltage vs. Output Current
ILC6391CP-30
EFFICIENCY: EFFI (%)
80
VIN = 3.0V
4.0 3.5 OUTPUT VOLTAGE: VOUT(V) 3.0 2.5
60
VIN = 1.2V VIN = 1.5V
VIN = 2.0V
VIN = 1.8V
40
20
L = 22H (CD54) R B = 300 CB = 0
VIN = 1.0V
VIN = 1.2V
VIN = 1.5V
2.0 1.5 1.0 0.5 0
L = 22H (CD105) RB = 300 CB = 0.1F
0 0
20
40
60
80
100
OUTPUT CURRENT I OUT (mA)
Efficiency vs. Output Current
100
20
40
60
80
100
ILC6391CP-30
OUTPUT CURRENT I OUT (mA)
Ripple Voltage vs. Output Current
80 EFFICIENCY: EFFI (%)
VIN = 1.8V VIN = 1.2V VIN = 1.5V
500
ILC6391CP-30
L = 22H (CD105) R B = 300 CB = 0
60
VIN = 1.0V
400 RIPPLE Vr (mV p-p) 40
300
VIN = 1.8V
20
L = 22H (CD105) R B = 300 C B = 0.1F
200
VIN = 1.5V
0 0
100
200
300
400
500
OUTPUT CURRENT I OUT (mA)
100
VIN = 1.2V
0 0 100 200 300 400 500 OUTPUT CURRENT I OUT (mA)
(c)2001 Fairchild Semiconductor Corporation
8
ILC6390/91
Typical Performance Characteristics General conditions for all curves
Efficiency vs. Output Current
120 100
VIN = 3.0V
Ripple Voltage vs. Output Current
500
ILC6391CP-50
ILC6391CP-50
L = 22H (CD54) R B = 500 CB = 0
EFFICIENCY: EFFI (%)
400 RIPPLE Vr (mV p-p)
80 60 40 20 0 0
L = 22H (CD105) RB = 300 CB = 0.1F VIN = 1.5V VIN = 2.0V
300
VIN = 3.0V
200
VIN = 2.0V
100
VIN = 1.5V
150
300
450
600
750
0 0 100 200 300 400 500 OUTPUT CURRENT I OUT (mA)
OUTPUT CURRENT I OUT (mA)
Output Voltage vs. Output Current Ripple Voltage vs. Output Current
7.0 6.0 OUTPUT VOLTAGE: VOUT(V) 5.0 4.0
VIN = 1.5V VIN = 2.0V VIN = 3.0V
ILC6391CP-50
500
ILC6391CP-30
L = 22H (CD105) R B = 300 C B = 0.1F
400 RIPPLE Vr (mV p-p)
VIN = 1.8V
300
3.0
VIN = 1.2V
200
VIN = 1.5V
2.0 1.0 0 0
L = 22H (CD54) RB = 300 CB = 0.1F
100
VIN = 1.2V
0 0 200 300 400 500 150 300 450 600 750 OUTPUT CURRENT I OUT (mA)
100
OUTPUT CURRENT I OUT (mA)
Output Voltage vs. Output Current
6 OUTPUT VOLTAGE VOUT (V) 5
VIN = 3.0V
Ripple Voltage vs. Output Current
600 500 RIPPLE Vr (mV p-p)
VIN = 3.0V
ILC6391CP-50
ILC6391CP-50
4 3 2 1 0 0
L = 22H (CD105) RB = 300 CB = 0.1F
VIN = 2.0V
400
VIN = 2.0V
VIN = 1.5V
300 200 100 0 0
VIN = 1.5V
L = 22H (CD105) RB = 300 CB = 0.1F
150
300
450
600
750
150
300
450
600
750
OUTPUT CURRENT I OUT (mA)
OUTPUT CURRENT I OUT (mA)
(c)2001 Fairchild Semiconductor Corporation
9
ILC6390/91
DISCLAIMER FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS. LIFE SUPPORT POLICY FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user.
www.fairchildsemi.com 10/15/01 0.0m 001 Stock#DSxxxxxxxx 2001 Fairchild Semiconductor Corporation
2. A critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

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