SP6653CP [EXAR]

Switching Regulator, 1A, PDIP8, PLASTIC, DIP-8;
SP6653CP
型号: SP6653CP
厂家: EXAR CORPORATION    EXAR CORPORATION
描述:

Switching Regulator, 1A, PDIP8, PLASTIC, DIP-8

开关 光电二极管
文件: 总13页 (文件大小:82K)
中文:  中文翻译
下载:  下载PDF数据表文档文件
®
SP6639/40/53  
5V/ 3.3V/ 3V Adjustable, High Efficiency, Low IQ,  
Step-Down DC-DC Converter  
FEATURES  
High Efficiency, 94%  
10µA Quiescent Current  
Low Current Shutdown Mode  
Low Battery Detector  
Preset Or Adjustable Output Voltage  
Low EMI Inductor Damping  
APPLICATIONS  
Cellular Phones  
Laptop Computers  
Distributed Power Systems  
5V to 3.3V Conversion  
Lithium-Ion Systems  
3 to 4 Alkaline Systems  
DESCRIPTION  
The SP6639/40/53 step-down switching regulators provide high efficiency over a wide range  
of input voltage, output voltage and output current. Duty cycle modulation is used to achieve  
efficiencies over 90% for input voltages from 3.3V to 7.5V. It features a no load quiescent  
current of only 10µA. The circuit contains a 1internal power MOSFET reducing the external  
component count to only one inductor, a schottky diode and the usual input and output  
capacitors. Theinternaloscillatorisshutdownwhenthecircuitisinregulationtoreducepower  
consumption. Internal inductor damping significantly reduces EMI.  
V
OUT  
1
2
3
4
8
7
6
5
SHDN  
VFB  
V+  
LBO  
LBI  
SP6639  
SP6640  
SP6653  
LX  
GND  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
1
Operating Temperature Ranges  
ABSOLUTE MAXIMUM RATINGS  
These are stress ratings only and functional operation  
of the device at these ratings or any other above those  
indicated in the operation sections of the specifications  
below is not implied. Exposure to absolute maximum  
rating conditions for extended periods of time may  
affect reliability and cause permanent damage to the  
device.  
SP6639.................................................0°C to +70°C  
Storage Temperature......................-65°C to +160°C  
Lead Temperature (soldering sec)................+300°C  
V+............................................................................9V  
LX..........................................(V+ - 16V) to (V+ +0.3V)  
LBI, LBO, VFB, SHDN, VOUT.......-0.3V to - (V+ +0.3V)  
LXOutput Current (Note 1).......................................1A  
LBO Output Current...........................................10mA  
Continuous Power Dissipation (TA = +70°C)  
Plastic DIP  
(derate 9.09mW/°C above +70°C....................727mW  
SO (derate 5.88mW/°C above +70°C .............471mW  
ELECTRICAL SPECIFICATIONS  
(V+ = 6V for the SP6639, V+ = 5V for the SP6640/6653, ILOAD = 0mA, TA = TMIN to TMAX, typical values are at TA = 25°C, circuit of figure 3 unless  
otherwise noted.)  
PARAMETER  
CONDITIONS  
MIN.  
TYP.  
MAX.  
UNITS  
DC CHARACTERISTICS  
Supply Voltage  
3.3  
4.0  
10  
7.5  
20  
V
µA  
Supply Current  
SHDN = V+, no load  
Output Voltage (Note 2)  
SP6639, V+ = 6.0V to 7.5V, 0mA < IOUT < 100mA  
SP6640, V+ = 4.0V to 7.5V, 0mA < IOUT < 100mA  
SP6653, V+ = 3.5V to 7.5V, 0mA < IOUT < 100mA  
IOUT = 100mA, L = 100µH  
4.80  
3.17  
2.88  
5.00  
3.30  
3.00  
0.3  
5.20  
3.43  
3.12  
V
V
Dropout Voltage  
IOUT = 100mA, L = 100µH  
91  
SP6639  
IOUT = 25mA, L = 470µH  
94  
IOUT = 100mA, L = 100µH  
87  
SP6640  
Efficiency  
%
IOUT = 25mA, L = 470µH  
91  
IOUT = 100mA, L = 100µH  
85  
SP6653  
IOUT = 25mA, L = 470µH  
89  
SP6639  
SP6640  
SP6653  
V+ = 6V, VOUT = 3V  
V+ = 4V, VOUT = 3.3V  
V+ = 4V, VOUT = 3V  
14.3  
57.0  
40.5  
40.5  
17.0  
16.0  
18.1  
45.0  
15.7  
62.9  
45.4  
47.0  
19.5  
18.5  
20.3  
55.0  
16.7  
72.0  
50.0  
52.0  
21.5  
20.5  
22.0  
68.0  
µs  
µsV  
µs  
Switch On-Time  
Switch Off-Time  
SP66XX KON Note 3  
SP6639  
SP6640  
SP6653  
V+ = 6V, VOUT = 3V  
V+ = 4V, VOUT = 3.3V  
V+ = 4V, VOUT = 3V  
µsV  
SP66XX KOFF Note 4  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
2
SPECIFICATIONS (continued)  
(V+ = 6V for the SP6639, V+ = 5V for the SP6640/6653, ILOAD = 0mA, TA = TMIN to TMAX, typical values are at TA=25°C,  
circuit of figure 3 unless otherwise noted.)  
PARAMETER  
CONDITIONS  
MIN.  
TYP.  
MAX.  
1.5  
UNITS  
V+ 6V, TA = +25OC, SP6639/40/53  
V+ 6V, TA = TMIN to TMAX, SP6639  
V+ 4V, TA = TMIN to TMAX, SP6640/53  
0.8  
2.5  
LX Switch On-Resistance  
LX Switch Leakage  
2.8  
TA = +25OC  
0.003  
1.0  
V+ = 7.5V, VLX = 0V  
µA  
TA = TMIN to TMAX  
30.0  
15.0  
VFB Bias Current  
VFB Dual-Mode Trip Point  
VFB Threshold  
VFB = 2V  
4.0  
50  
nA  
mV  
V
1.26  
1.28  
2
1.30  
10  
LBI Bias Current  
LBI Threshold  
VLBI = 2V  
nA  
V
1.26  
0.8  
1.28  
2.5  
1.30  
SP6639  
LBO Sink Current  
VLBO = 0.4V  
mA  
SP6640/SP6653  
0.4  
1.2  
µA  
µs  
LBO Leakage Current  
LBO Delay  
VLBO = 7.5V  
0.001  
25  
0.1  
50mV overdrive  
SHDN Threshold  
SHDN Pull-Up Current  
0.80  
0.10  
1.15  
0.20  
2.00  
0.40  
V
µA  
SHDN = 0V  
Note 1: Peak Inductor current must be limited to 600mA by using an inductor of 100µH or greater.  
Note 2: Output guaranteed by correlation to measurements of device parameters (i.e. switch on-resistance, on-times, off-times,  
and output voltage trip points).  
Note 3: KON = tON* (V+ -Vout). For the SP6639 V+ = 6V to 7.5V, Vout = 3V to 5V; for the SP6640 V+ = 4V to 7.5V, Vout = 3.3V;  
for the SP6653 V+ = 4V to 7.5V, Vout = 3V.  
Note 4: KOFF = TOFF * Vout. For the SP6639 V+ = 6V to 7.5V, Vout = 3V to 5V; for the SP6640 V+ = 4V to 7.5V, Vout = 3.3V;  
for the SP6653 V+ = 4V to 7.5V, Vout = 3V.  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
3
TYPICAL PERFORMANCE CHARACTERISTICS  
(Circuit of Figure 3. Internal Feedback, L = 100µH, TA = +25°C, unless otherwise noted)  
Efficiency vs. Output Current  
Efficiency vs. Output Current  
V+ = 7.5V, L = 470µH  
V+ = 7.5V, L = 100µH  
95.0  
90.0  
85.0  
80.0  
75.0  
70.0  
95.0  
90.0  
85.0  
80.0  
75.0  
70.0  
SP6639  
SP6640  
SP6653  
SP6639  
SP6640  
SP6653  
0.1  
1.0  
10.0  
100.0  
1000.0  
0.1  
1.0  
10.0  
100.0  
Output Current (mA)  
Output Current (mA)  
Efficiency vs. Output Current  
Efficiency vs. Output Current  
L = 470µH  
L=100µH  
100.0  
95.0  
100.0  
95.0  
90.0  
85.0  
80.0  
75.0  
70.0  
90.0  
85.0  
80.0  
75.0  
70.0  
SP6639, V+ = 6V  
SP6640, V+ = 4V  
SP6653, V+ = 4V  
SP6639, V+ = 6V  
SP6640, V+ = 4V  
SP6653, V+ = 4V  
0.1  
1.0  
10.0  
100.0  
1000.0  
0.1  
1.0  
10.0  
100.0  
Output Current (mA)  
Output Current (mA)  
Efficiency vs. Input Voltage  
Efficiency vs. Input Voltage  
L = 470µH, I  
= 30mA  
L = 100µH, I  
= 100mA  
OUT  
OUT  
100.0  
95.0  
100.0  
95.0  
90.0  
85.0  
80.0  
75.0  
70.0  
90.0  
85.0  
80.0  
75.0  
70.0  
SP6639  
SP6640  
SP6653  
SP6639  
SP6640  
SP6653  
3.0  
4.0  
5.0  
6.0  
7.0  
8.0  
3.0  
4.0  
5.0  
6.0  
7.0  
8.0  
Supply Voltage (V)  
Supply Voltage (V)  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
4
TYPICAL PERFORMANCE CHARACTERISTICS  
(Circuit of Figure 3. Internal Feedback, L = 100µH, TA = +25°C, unless otherwise noted)  
Maximum Output Current vs. Input Voltage  
Maximum Output Current vs. Input Voltage  
L = 470µH  
L = 100µH  
60  
200  
180  
160  
140  
120  
100  
40  
50  
40  
30  
20  
10  
0
SP6639  
SP6640  
SP6653  
SP6639  
SP6640  
SP6653  
20  
40  
20  
0
3.0  
4.0  
5.0  
6.0  
7.0  
8.0  
3.0  
4.0  
5.0  
6.0  
7.0  
8.0  
Supply Voltage (V)  
Supply Voltage (V)  
SP6653 Output Voltage Ripple  
40  
35  
30  
25  
20  
15  
10  
L = 100µH, I  
L = 220µH, I  
L = 470µH, I  
= 100mA  
= 60mA  
= 30mA  
OUT  
OUT  
OUT  
5
0
3.0  
4.0  
5.0  
6.0  
7.0  
8.0  
Supply Voltage (V)  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
5
PIN DESCRIPTION  
NAME  
FUNCTION  
PIN  
Sense input for regulated-output operation. Internally connected to an on-  
chip voltage divider and to the variable duty-cycle, on demand oscillator. It  
must be connected to the external regulated output.  
VOUT  
LBO  
1
Low-Battery Output. An open-drain N-channel MOSFET sinks current when  
the voltage at LBI drops below 1.28V.  
2
Low Battery Input. When the voltage at LBI drops below 1.28V, LBO sinks  
current.  
LBI  
GND  
LX  
3
4
5
6
Ground  
Drain of a PMOS power switch that has its source connected to V+. LX  
drives the external inductor, which provides current to the load.  
V+  
Positive Supply-Voltage Input. Should not exceed 9V  
Dual-Mode Feedback Pin. When VFB is grounded, the internal voltage  
divider sets the output to 5V (SP6639), 3.3v (SP6640), or 3V (SP6653).  
For adjustable operation, connect VFB to an external voltage divider.  
VFB  
7
8
Shutdown Input- active low. When pulled below 0.8V, the LX power switch  
stays off, shutting down the regulator. When the shutdown input is above  
2V, the regulator stays on. Tie SHDN to V+ if shutdown mode is not used.  
SHDN  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
6
Figure 2 shows what happens to the ideal circuit  
ofFigure1iftheswitchturnsonwitha66%duty  
cycle and V+ =3/2 VOUT. The inductor current  
rises more slowly than it falls because the mag-  
nitude of the voltage applied during tON is less  
than that applied during tOFF. Varying the duty  
cycle and switching frequency keeps the peak  
current constant as input voltage varies. The  
GETTING STARTED  
Designing power supplies with the SP6639/40/  
53 is easy. The few required external compo-  
nents are readily available. The most general  
applications use the following components:  
1) Capacitors: For the input and output filter  
capacitors, try using electrolytics in the 100µF  
range, or use low-ESF capacitors to minimize  
output ripple. Capacitor values are not critical.  
SP6639/40/53 control the switch ( tON and tOFF  
according to the following equations:  
)
2) Diode: Use the popular 1N5817 equivalent  
Schottky diode.  
Equation (1) tON = 50µsV/ (V+ - VOUT  
Equation (2) tOFF = 50µsV/ VOUT  
Equation (3)IPEAK = 50µsV/L  
)
3) Inductor: For the highest output current,  
choose a 100µH inductor with an incremental  
saturation current rating of at least 600mA. To  
obtain the highest efficiencies and smallest size,  
refer to the Inductor Selection section.  
These three equations ensure constant peak cur-  
rents for a given inductor value, across all output  
voltages (ignoring the voltage drop across the  
diode (D1) and the resistive losses in the switch  
and inductor.) The variable duty cycle also  
ensures that the current through the inductor  
discharges to zero at the end of each pulse.  
DETAILED DESCRIPTION  
Figure 1 shows a simplified, step-down DC-DC  
converter. When the switch is closed, a voltage  
equal to (V+ - VOUT) is applied to the inductor.  
The current through the inductor ramps up, stor-  
ing energy in the inductor's magnetic field. The  
same current also flows into the output filter  
capacitor and load. When the switch opens, the  
current continues to flow through the inductor in  
the same direction, but must also flow through  
the diode. The inductor alone supplies current to  
the load when the switch is open. The current  
decaystozeroastheenergystoredintheinductor's  
magnetic field is transferred to the output filter  
capacitor and the load.  
I AT 200mA/DIV  
L
0A  
0V  
V AT5V/DIV  
L
SWITCH ON  
SWITCH ON  
SWITCH OFF  
SWITCH OFF  
IL  
L
Figure 2. Simplified Step-Down Converter Operation  
VL  
Figure 3 shows the SP6639/40/53 block dia-  
gram and a typical connection in which 7V is  
converted to 5V (SP6639), 3.3V (SP6640), or  
3.0V (SP6653). The sequence of events in this  
application is as follows:  
+
V
OUT  
V
+
+
C
OUT  
Figure 1. Simplified Step-Down Converter  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
7
When the output dips:  
Low-Battery Detector  
1) The error comparator switches high.  
2) The internal oscillator starts and connects  
to the gate of the LX output driver.  
3) LX turns on and off according to tON and  
tOFF, charging and discharging the inductor,  
and supplying current to the output (as  
described above.)  
The low battery detector compares the voltage  
on the LBI input with the 1.28V reference. LBO  
goes low whenever the input voltage at LBI is  
less than 1.28V. Set the low-battery detection  
voltage with resistors R1 and R2 (Figure 3) as  
determined by the following formula:  
When the output voltage recovers:  
1) The comparator switches low.  
2) After a full charge and discharge cycle, LX  
turns off.  
R1 = R2 ( VLB/ LBI Threshold) – 1  
where R2 is any resistance in the 10krange  
(typically 100k), the LBI threshold is typi-  
cally 1.28V and the VLB is the desired low-  
batterydetectionvoltage. Thelow-batterycom-  
parator remains active in shutdown mode.  
3) The oscillator shuts down to save power.  
Fixed or Adjustable Output  
For operation at the present output voltage,  
connect VFB to GND; no external resistors are  
required. For other output voltages, use an  
external voltage divider. Set the output voltage  
using R3 and R4 as determined by the following  
formula.  
Shutdown Mode  
BringingSHDNbelow0.8VplacestheSP6639/  
40/53 in shutdown mode. LX becomes high  
impedance, and the voltage at VOUT falls to  
zero. The time required for the output to rise to  
its nominal regulated voltage when brought out  
of shutdown (start-up time) depends on the  
inductor value, input voltage, and load current  
(see the Start-Up Time vs Output Current graph  
in the Typical Operating Characteristics). The  
low-battery comparator remains active in shut-  
down mode.  
R3 = R4 (VOUT / VFB Threshold) – 1  
where R4 is any resistance in the 10krange  
(typically 100k), the LBI threshold is typi-  
cally 1.28V.  
Input +5.5V to +7.5V (SP6639),  
+3.8V to 7.5V (SP6640), +3.5V to 7.5V (SP6653)  
6
8
5V, 3.3V, OR 3.0V  
AT 100mA  
V
+
SHDN  
L
X
5
1
+
C
IN  
L = 100µH  
33µF  
+1.28V  
1N5817  
BANDGAP  
REFERENCE  
VARIABLE  
FREQUENCY  
AND  
DUTY-CYCLE  
OSCILLATOR  
ERROR  
COMPARATOR  
+
V
OUT  
R1  
-
+
LOW-BATTERY  
COMPARATOR  
C
OUT  
100µF  
+
MODE-SELECT  
COMPARATOR  
3
2
-
LBI  
-
LBO  
50mV  
+
-
+
R2  
GND  
4
VFB  
7
Figure 3. Block Diagram  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
8
Inductorseriesresistanceaffectsbothefficiency  
and dropout voltage. A high series resistance  
severely limits the maximum current available  
at lower input voltages. Output currents up to  
225mA are possible if the inductor has low  
series resistance. Inductor and series switch  
resistance form an LR circuit during tON. If the  
L/R time constant is less than the oscillator t ,  
the inductor's peak-current will fall short of tOhNe  
INPUT  
+4.0V to +11.5V  
L = 100µF  
OUTPUT  
+
5
LX  
6
8
V+  
1N5817  
C
OUT  
100µF  
SHDN  
1
7
R3  
+
VOUT  
C
IN  
SP6639  
SP6640  
SP6653  
100µF  
VFB  
GND  
4
LBI  
R4  
desired IPEAK  
.
3
To maximize efficiency, choose the highest-  
value inductor that will provide the required  
output current over the whole range of your  
input voltage (see Typical Operating Character-  
istics).Inductorswithpeakcurrentsinthe600mA  
range do not need to be very large. They are  
about the size of a 1W resistor, with surface  
mount versions less than 5mm in diameter.  
Table 1 lists the suppliers of inductors suitable  
for use with the SP6639/40/53.  
Figure 4. Adjustable-Output Operation  
Inductor Selection  
When selecting an inductor, consider these four  
factors: peak-current rating, inductance value,  
series resistance, and size. It is important not to  
exceed the inductor's peak-current rating. A  
saturated inductor will pull excessive currents  
through SP6639/40/53's switch, and may cause  
damage. Avoid using RF chokes or air-core  
inductors since they have very low peak-current  
ratings. Electromagnetic interference must not  
upset nearby circuitry or the regulator IC.  
Output Filter Capacitor  
The SP6639/40/53 output ripple has two com-  
ponents. One component results from the varia-  
tion in stored charge on the filter capacitor with  
each LX pulse. The other is the product of the  
current into the capacitor and the capacitor’s  
equivalent series resistance (ESR).  
Recall that the inductance value determines  
IPEAK for all input voltages (Equation 3). If  
there are no resistive losses and the diode is  
ideal, the maximum average current that can be  
drawn from the SP6639/40/53 will be one-half  
IPEAK. With the real losses in the switch,  
inductor, and diode taken into account, the real  
maximum output current typically varies from  
90% to 50% of the ideal. The following steps  
describeaconservativewaytopickanappropri-  
ate inductor.  
The amount of charge delivered in each oscilla-  
torpulseisdeterminedbytheinductorvalueand  
input voltage. It decreases with larger induc-  
tance, but increases as the input voltage lessens.  
As a general rule, a smaller amount of charge  
delivered in each pulse results in less output  
ripple.  
Step1: Decideonthemaximumrequiredoutput  
With low-cost aluminum electrolytic capaci-  
tors, the ES-induced ripple can be larger than  
that caused by the charge variation. Conse-  
quently, high-quality aluminum-electrolytic or  
tantalum filter capacitors should be considered  
to minimize output ripple. Best results at  
reasonable cost are typically achieved with an  
aluminum-electrolytic capacitor in the 100µF  
range, in parallel with a 0.1µF ceramic  
capacitor (see Table 1).  
current, in amperes: IOUTMAX  
Step 2: IPEAK = 4 X IOUTMAX  
Step 3: L = 50/IPEAK. L will be in mH. Do not  
use an inductor of less than 100mH.  
Step 4: Make sure that IPEAK does not exceed  
0.6A or the inductor’s maximum cur-  
rent rating whichever is lower.  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
9
Layout  
External Diode  
SeveraloftheexternalcomponentsinaSP6639/  
40/53 circuit experience peak currents up to  
600mA. Whenever one of these components  
connects to ground, there is a potential for  
ground bounce. Ground bounce occurs when  
high currents flow through the parasitic resis-  
tance of PC board traces. What one component  
interprets as ground can differ from the IC’s  
ground by several millivolts. This may increase  
the SP6639/40/53’s output ripple, since the er-  
ror comparator (which is referenced to ground)  
will generate extra switching pulses when they  
are not needed. It is essential that the input filter  
capacitor’s ground lead, the SP6639/40/53’s  
GND pin, the diode’s anode, and the output  
filter capacitor’s ground lead are as close to-  
gether as possible.  
In most SP6639/40/53 circuits, the current in the  
external diode (D1, Figure 3) changes abruptly  
fromzerotoitspeakvalueeachtimeLXswitches  
off. To avoid excessive losses, the diode must  
have a fast turn-on time. For low-power circuits  
with peak currents less than 100mA, signal di-  
odes such as the 1N4148 perform well. The  
1N5817diodeworkswellforhighpowercircuits  
orformaximumefficiencyatlowpower. 1N5817  
equivalent diodes are also available in surface  
mountpackages(Table1). Althoughthe1N4001  
and other general-purpose rectifiers are rated for  
high currents, they are unacceptable because  
theirslowturn-offtimesresultinexcessivelosses.  
Minimum Load  
Underno-loadconditions, becauseleakagefrom  
the PMOS power switch (see the LX Leakage  
Current vs. Temperature graph in the Typical  
Operating Characteristics) and from the internal  
resistor from V+ to VOUT, leakage current may  
be supplied to the output capacitor, even when  
the switch is off. This will usually not be a  
problem for a 5V output at room temperature,  
since the diode’s reverse leakage current and the  
feedback resistor’s current typically drain the  
excess. However, if the diode leakage is very  
low(whichcanoccuratlowtemperaturesand/or  
small output voltages), charge may build up on  
the output capacitor, making it rise above its set  
point. If this happens, add a small load resistor  
capacitor (typically 1MW) to the output to pull  
a few extra microamps of current from the out-  
put capacitor.  
Inverter Configuration  
Figure 5 shows the SP6639/40/53 in a floating  
ground configuration. By tying what would  
normally be the output to the supply-voltage  
ground, the IC’s GND pin is forced to regulated  
–5V(SP6639),3.3V(SP6640),or3V(SP6653).  
Avoidexceedingthemaximumdifferentialvolt-  
age of 7.5V from V+ to VOUT. Other negative  
voltages can be generated by placing a voltage  
divideracrossCOUTandconnectingthetappoint  
to VFB in the same manner as the normal step-  
down configuration.  
Two AA Batteries to 5V, 3.3V or 3V  
Forbattery-poweredapplications,wherethesig-  
nal ground does not have to correspond to the  
power-supply ground, the circuit in Figure 5  
generates 5V (SP6639), 3.3V (SP6640), or 3V  
(SP6653) from a pair of AA batteries. Connect  
the VIN ground point to your system’s input, and  
connect the output to your system’s ground in-  
put. This configuration, since the IC’s internal  
power FET has VIN + VOUT of gate drive.  
6
8
+
-
+
V
IN  
V
+
SHDN  
C
IN  
100µF  
L = 100µF  
5
LX  
1N5817  
SP6639  
SP6640  
SP6653  
1
V
OUT  
C
OUT  
100µF  
+
-
-5V  
-3.3V  
OR -3V  
VFB  
7
GND  
4
Figure 5. Inverting Configuration  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
10  
PACKAGE: 8 LEAD PLASTIC  
DUAL–IN–LINE  
(NARROW)  
E1  
E
D1 = 0.005" min.  
(0.127 min.)  
A1 = 0.015" min.  
(0.381min.)  
D
A = 0.210" max.  
(5.334 max).  
C
A2  
Ø
L
B1  
B
e
= 0.300 BSC  
(7.620 BSC)  
e = 0.100 BSC  
(2.540 BSC)  
A
ALTERNATE  
END PINS  
(BOTH ENDS)  
DIMENSIONS (Inches)  
Minimum/Maximum  
(mm)  
8–PIN  
0.115/0.195  
(2.921/4.953)  
A2  
0.014/0.022  
(0.356/0.559)  
B
0.045/0.070  
B1  
C
(1.143/1.778)  
0.008/0.014  
(0.203/0.356)  
0.355/0.400  
(9.017/10.160)  
D
0.300/0.325  
(7.620/8.255)  
E
0.240/0.280  
E1  
L
(6.096/7.112)  
0.115/0.150  
(2.921/3.810)  
0°/ 15°  
(0°/15°)  
Ø
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
11  
PACKAGE: 8 LEAD PLASTIC  
SMALL OUTLINE (SOIC)  
(NARROW)  
E
H
h x 45°  
D
A
Ø
A1  
L
e
B
DIMENSIONS (Inches)  
Minimum/Maximum  
(mm)  
8–PIN  
A
A1  
B
D
E
0.053/0.069  
(1.346/1.748)  
0.004/0.010  
(0.102/0.249  
0.014/0.019  
(0.35/0.49)  
0.189/0.197  
(4.80/5.00)  
0.150/0.157  
(3.802/3.988)  
e
0.050 BSC  
(1.270 BSC)  
H
h
0.228/0.244  
(5.801/6.198)  
0.010/0.020  
(0.254/0.498)  
L
0.016/0.050  
(0.406/1.270)  
Ø
0°/8°  
(0°/8°)  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001Sipex Corporation  
12  
ORDERING INFORMATION  
Temperature Range  
Model  
Package Type  
SP6639CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC  
SP6640CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC  
SP6653CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC  
SP6639CP ............................................... 0˚C to +70˚C .............................................. 8-Pin PDIP  
SP6640CP ............................................... -0˚C to +70˚C ............................................. 8-Pin PDIP  
SP6653CP ............................................... -0˚C to +70˚C ............................................. 8-Pin PDIP  
Please consult the factory for pricing and availability on a Tape-On-Reel option.  
Co rp o ra tio n  
SIGNAL PROCESSING EXCELLENCE  
Sipex Corporation  
Headquarters and  
Sales Office  
22 Linnell Circle  
Billerica, MA 01821  
TEL: (978) 667-8700  
FAX: (978) 670-9001  
e-mail: sales@sipex.com  
Sales Office  
233 South Hillview Drive  
Milpitas, CA 95035  
TEL: (408) 934-7500  
FAX: (408) 935-7600  
Sipex Corporation reserves the right to make changes to any products described herein. Sipex 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.  
Rev. 2/23/01  
SP6639/40/53 5/ 3.3/ 3V, Adj High Efficiency, Low IQ Step-Down DC-DC Converter  
© Copyright 2001 Sipex Corporation  
13  

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