SP6640CN [SIPEX]
Switching Regulator, 1A, PDSO8, SOIC-8;
| 型号： | SP6640CN |
| 厂家： | 
SIPEX CORPORATION |
| 描述： | Switching Regulator, 1A, PDSO8, SOIC-8 开关 光电二极管 |
| 文件： | 总14页 (文件大小：89K) |
| 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, 94% Efficiency
■ 100mA Output Current
■ 10µA Quiescent Current
■ Low Current Shutdown Mode
■ Low Battery Detector
■ Preset 5.0V, 3.3V, 3.0V or Adjustable
Output Voltage
■ Low EMI Inductor Damping
■ 3.2V-11.5V Wide Input Range
■ Only 4 External Components
V
OUT
1
2
3
4
8
7
6
5
SHDN
VFB
V+
LBO
LBI
SP6639
SP6640
SP6653
LX
GND
APPLICATIONS
■ Cellular Phones
■ Laptop Computers
■ Distributed Power Systems
■ 5V to 3.3V Conversion
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 3.2V to 11.5V. It features a no load quiescent
current of only 10µA. The circuit contains an internal 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. This product is offered in
an 8 lead nSOIC package.
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
100µF
SP6639
SP6640
SP6653
VFB
GND
4
LBI
R4
3
Adjustable Output Operation
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex 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+............................................................................12V
LX..........................................(V+ - 12V) to (V+ +0.3V)
LBI,LBO,VFB,SHDN,VOUT...............-0.3Vto(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
3.2
4.0
10
11.5
20
V
µA
Supply Current
SHDN = V+, no load
Output Voltage (Note 2)
SP6639, V+ = 5.2V to 11.5V, 0mA < IOUT < 100mA
SP6640, V+ = 3.5V to 11.5V, 0mA < IOUT < 100mA
SP6653, V+ = 3.2V to 11.5V, 0mA < IOUT < 100mA
IOUT = 100mA, L = 100µH
4.80
3.17
2.88
5.00
3.30
3.00
0.1
5.20
3.43
3.12
0.2
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 = 5V
V+ = 4V, VOUT = 3.3V
V+ = 4V, VOUT = 3V
40.5
57.0
40.5
40.5
9.0
47.0
62.9
45.4
47.0
11.0
16.7
18.3
55.0
52.0
72.0
50.0
52.0
13.6
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 = 5V
V+ = 4V, VOUT = 3.3V
V+ = 4V, VOUT = 3V
13.5
15.0
45.0
µsV
SP66XX KOFF Note 4
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 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
Ω
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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
3
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 3. Internal Feedback, L = 100µH, TA = +25°C, unless otherwise noted)
SP6639 Efficiency vs. Load and Supply
SP6639 Efficiency vs. Load and Supply
L = 100µH
L = 470µH
100.0
95.0
90.0
85.0
80.0
100.0
95.0
90.0
85.0
80.0
Vi = 5.2V
Vi = 6.0V
Vi = 5.2V
Vi = 6.0V
75.0
70.0
65.0
75.0
70.0
65.0
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
1.0
10.0
100.0
1000.0
1.0
10.0
100.0
Output Current (mA)
Output Current (mA)
SP6640 Efficiency vs. Load and Supply
SP6640 Efficiency vs. Load and Supply
L = 100µH
L = 470µH
100.0
95.0
90.0
85.0
80.0
100.0
95.0
90.0
85.0
80.0
Vi = 3.6V
Vi = 6.0V
Vi = 3.6V
Vi = 6.0V
75.0
70.0
65.0
75.0
70.0
65.0
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
1.0
10.0
100.0
1000.0
1.0
10.0
100.0
Output Current (mA)
Output Current (mA)
SP6653 Efficiency vs. Load and Supply
SP6653 Efficiency vs. Load and Supply
L = 470µH
L = 100µH
100.0
95.0
90.0
85.0
80.0
100.0
95.0
90.0
85.0
80.0
Vi = 3.6V
Vi = 6.0V
Vi = 3.6V
Vi = 6.0V
75.0
70.0
65.0
75.0
70.0
65.0
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
Vi = 8.0V
Vi = 10.0V
Vi = 11.5V
1.0
10.0
100.0
1000.0
1.0
10.0
100.0
Output Current (mA)
Output Current (mA)
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 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
250
200
150
70
60
50
40
30
20
100
50
0
SP6639
SP6640
SP6653
SP6639
SP6640
SP6653
10
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
9.0
10.0
11.0
9.0
10.0
11.0
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
9.0
10.0 11.0
Supply Voltage (V)
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex 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 12V
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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
6
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,tryusingelectrolyticsinthe100µF
range, or use low-ESF capacitors to minimize
output ripple. Capacitor values are not critical.
2. Diode: Use the popular 1N5817 equivalent
Schottky diode.
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.
SP6639/40/53 control the switch ( tON and tOFF
according to the following equations:
)
47µsV
(V+ – VOUT
tON
=
(1)
)
55µsV
VOUT
tOFF
=
(2)
(3)
50µsV
L
IPEAK
=
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 off-time constant (KOFF) be-
ing slightly greater than the on-time constant
(KON)ensuresthatthecurrentthroughtheinduc-
tor discharges to zero at the end of each pulse.
Full-cycle logic ensures that once a charge/
discharge cycle has started it will finish. This
again makes sure that the inductor current is
discharged to zero. At this point (as detected by
an internal inductor damping comparator) the
coil is shunted by an internal FET, effectively
reducing the ringing on the LX node (and it’s
associated EMI) to near zero.
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.
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:
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
I AT 200mA/DIV
L
0A
0V
IL
L
V AT5V/DIV
L
VL
+
V
OUT
V
+
+
C
OUT
SWITCH ON
SWITCH ON
SWITCH OFF
SWITCH OFF
Figure 1. Simplified Step-Down Converter
Figure 2. Simplified Step-Down Converter Operation
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex 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
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:
t
OFF, charging and discharging the induc-
tor, and supplying current to the output (as
described above.)
VLB
When the output voltage recovers:
1) The comparator switches low.
2) After a full charge and discharge cycle, LX
turns off.
R1 = R2
– 1
(
)
LBI Threshold
where R2 is any resistance in the 10kΩ range
(typically 100kΩ), 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
Shutdown Mode
BringingSHDNbelow0.8VplacestheSP6639/
40/53 in shutdown mode. LX becomes high
impedance, andthevoltageatVOUT fallstozero.
The time required for the output to rise to its
nominal regulated voltage when brought out of
shutdown (start-up time) depends on the induc-
tor value, input voltage, and load current. The
low-battery comparator remains active in shut-
down mode.
formula.
VOUT
R3 = R4
– 1
(
)
VFB Threshold
where R4 is any resistance in the 10kΩ range
(typically 100kΩ), the LBI threshold is typi-
cally 1.28V.
Input +5.5V to +11.5V (SP6639),
+3.5V to 11.5V (SP6640), +3.2V to 11.5V (SP6653)
SHDN
8
V+
6
5V, 3.3V or 3.0V
LX
at 100mA
LX
+
C
IN
100µF
Internal
MOSFET
Switch
5
L = 100µH
Variable Frequency and
Duty Cycle Oscillator with
Full-Cycle Logic
MBR1530
+
_
Inductor
Damping
Comparator
50mV
V
OUT
1
1.28V
Bandgap
Reference
R1
+
_
Error
Comparator
1.28V
REF
Low-Battery
Comparator
C
OUT
+
–
+
LBI
100µF
3
LBO
2
Mode Select
Comparator
50mV
-
+
R2
GND
4
V
FB
7
Figure 3. Block Diagram
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
8
Step1: Decideonthemaximumrequiredoutput
INPUT
+4.0V to +11.5V
current, in amperes: IOUTMAX
L = 100µF
OUTPUT
+
5
LX
Step 2: IPEAK = 4 X IOUTMAX
6
8
V+
1N5817
C
OUT
100µF
SHDN
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.
1
7
R3
+
VOUT
C
IN
100µF
SP6639
SP6640
SP6653
VFB
GND
4
LBI
R4
3
Inductorseriesresistanceaffectsbothefficiency
and dropout voltage. A high series resistance
severely limits the maximum current available
at lower input voltages. Output currents up to
150mA are possible if the inductor has low
series resistance. Inductor and series switch
resistance form an LR circuit during tON. If the
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. Fer-
rite-bobbin types work for most digital circuits;
toroids or pot cores work well for EMI-sensitive
analog circuits.
L/R time constant is less than the oscillator tON
the inductor's peak-current will fall short of the
desired IPEAK
,
.
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.
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.
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
9
INDUCTORS - SURFACE MOUNT
Inductor Specification
Inductance
(uH)
Manufacturer/
Part No.
Series R
(Ω)
Isat
(A)
Size LxWxH
(mm)
Inductor Type
Manufacturer
Website
100
220
100
220
470
100
220
470
Sumida CD54-101
Sumida CD54-221
0.63
1.50
0.70
1.80
4.20
0.28
0.61
1.27
0.52
0.35
0.56
0.32
0.24
1.20
0.80
0.50
5.2x5.8x4.5
5.2x5.8x4.5
5.0x5.7x4.7
5.0x5.7x4.7
5.0x5.7x4.7
Unshielded Ferrite Core www.sumida.com
Unshielded Ferrite Core www.sumida.com
Unshielded Ferrite Core www.murata.com
Unshielded Ferrite Core www.murata.com
Unshielded Ferrite Core www.murata.com
Murata LQN6C101M04
Murata LQN6C221M04
Murata LQN6C471M04
Coilcraft DO3316P-104
Coilcraft DO3316P-224
Coilcraft DO3316P-474
12.9x9.4x5.0 Unshielded Ferrite Core www.coilcraft.com
12.9x9.4x5.0 Unshielded Ferrite Core www.coilcraft.com
12.9x9.4x5.0 Unshielded Ferrite Core www.coilcraft.com
CAPACITORS - SURFACE MOUNT & THROUGH HOLE
Capacitor Specification
Capacitance
(uF)
Manufacturer/
Part No.
ESR Ripple Current Size LxWxH Voltage
Capacitor
Type
Manufacturer
Website
Ω (max) (A) @ 25C
(mm)
7343H
8Dx10L
(V)
10
16
100
100
SANYO 10TPA100M
SANYO 16SA100M
0.08
0.03
1.2
2.7
SMT Tant. www.sanyovideo.com
OS-CON
www.sanyovideo.com
SCHOTTKY DIODE - SURFACE MOUNT & THROUGH HOLE
Diode Specification
Manufacturer/
Part No.
V
IF(AV)
(A)
0.5
1.0
Size LxWxH Reverse V Package
Manufacturer
Website
F @ IF
(V)
(mm)
(V)
30
20
Type
On-Semi MBR0530
On-Semi 1N5817
0.43
0.45
2.8x1.8x1.3
3Dx6.5L
SOD-123
Axial-Lead
www.onsemi.com
www.onsemi.com
Table 1: Component Selection
Output Filter Capacitor
With low-cost aluminum electrolytic capaci-
tors, the ESR-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).
TheSP6639/40/53outputripplehastwocompo-
nents. Onecomponentresultsfromthevariation
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).
The amount of charge delivered in each oscilla-
tor pulse is determined by the inductor value and
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.
Rev. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
10
to pull a few extra microamps of current from
the output capacitor.
Layout
External Diode
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
1N5817 diode works well for high power cir-
cuits or for maximum efficiency at low power.
1N5817 equivalent diodes are also available in
surface mount packages(Table 1). Althoughthe
1N4001 and other general-purpose rectifiers are
rated for high currents, they are unacceptable
because their slow turn-off times result in exces-
sive losses.
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.
Minimum Load
Underno-loadconditions,becauseleakagefrom
the PMOS power switch (see the LX Leakage
Current vs. Temperature graph in the Typical
OperatingCharacteristics)andfromtheinternal
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,
sincethediode’sreverseleakagecurrentandthe
feedback resistor’s current typically drain the
excess. However, if the diode leakage is very
low (which can occur at low temperatures and/
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
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), or –3V
(SP6653). Avoid exceeding the maximum dif-
ferential voltage of 11.5V from V+ to VOUT
.
Other negative voltages can be generated by
placing a voltage divider across COUT and con-
necting the tap point 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 has the added advantage
of reduced resistance, 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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
11
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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
12
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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
13
ORDERING INFORMATION
Temperature Range
Model
Package Type
SP6639CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC
SP6639CN/TR ......................................... 0˚C to +70˚C ................... (Tape & Reel) 8-Pin NSOIC
SP6640CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC
SP6640CN/TR ......................................... 0˚C to +70˚C ................... (Tape & Reel) 8-Pin NSOIC
SP6653CN ............................................... 0˚C to +70˚C ........................................... 8-Pin NSOIC
SP6653CN/TR ......................................... 0˚C to +70˚C ................... (Tape & Reel) 8-Pin NSOIC
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. 8/1/01
SP6639/40/53 5V, 3.3V, 3V Adj, High Efficiency, Low IQ Step-Down DC-DC Converter
© Copyright 2001Sipex Corporation
14
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