SS6638
1-Cell, 3-Pin, Step-Up DC/DC Converter
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FEATURES
•
•
•
•
•
•
•
Guaranteed start-up from less than 0.9 V.
High efficiency.
Low quiescent current.
Fewer external components needed.
Low ripple and low noise.
Fixed output voltage: 2.7, 3.0V, 3.3V, and 5V.
Space-saving package: SOT-89 and TO-92.
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GENERAL DESCRIPTION
The SS6638 is a high efficiency step-up DC/DC
converter for applications using 1 to 4 NiMH battery cells.
Three external components are required to deliver a
fixed output voltage of 2.7, 3.0V, 3.3V, or 5V. The
SS6638 starts up from less than 0.9V input with 1mA
load. The Pulse Frequency Modulation scheme offers
optimized performance for applications with light output
loading and low input voltages. The output ripple and
noise are lower than with circuits operating in PSM
mode.
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APPLICATIONS
•
•
•
•
•
•
Pagers.
Cameras.
Wireless Microphones.
Pocket Organizers.
Battery Backup Suppliers.
Portable Instruments.
The PFM control circuit operating up to 100 KHz
switching rate results in smaller passive components.
The space-saving SOT-89 and TO-92 packages make
the SS6638 an ideal choice of DC/DC converter for
space-conscious
applications,
such
as
pagers,
electronic cameras, and wireless microphones.
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TYPICAL APPLICATION CIRCUIT
V
IN
L1
100µH
D1
GS SS12
V
OUT
+
SS6638-27
SS6638-30
SS6638-33
C1
SW
SS6638-50
22µF
GND
+
VOUT
C2
47µF
One Cell Step-Up DC/DC Converter
Rev.2.01 6/26/2003
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SS6638
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ORDERING INFORMATION
SS6638-XXCXXX
PIN CONFIGURATION
PACKING TYPE
TR: TAPE & REEL
BG: BAG
PACKAGE TYPE
X: SOT-89
Z: TO-92
OUTPUT VOLTAGE
27: 2.7V
30: 3.0V
33: 3.3V
50: 5.0V
EX: SS6638-27CXTR
à
2.7V Version, in SOT-89 Package in
Tape and Reel Packing
SOT-89
TOP VIEW
1: GND
2: VOUT
3: EXT
1
2
3
TO-92
TOP VIEW
1: GND
2: VOUT
3: EXT
1
2
3
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ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VOUT Pin) ……………….………………………………………………….12V
SW pin Voltage ……………………………………………………………............................12V
SW pin Switch Current …………………………………………………………………… 600mA
Operating Temperature Range
……………………………………………….-40°C to 85°C
Storage Temperature Range ………………………………………………… -65°C to 150
°C
Lead Temperature (Soldering 10 Sec.) …………………………………………………260°C
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TEST CIRCUIT
SS6638
100
2.5V
VOUT
GND
SW
FOUT
Oscillator Test Circuit
Rev.2.01 6/26/2003
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SS6638
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ELECTRICAL CHARACTERISTICS
(T
A
=25°C, I
OUT
=10mA, unless otherwise specified)
PARAMETER
TEST CONDITIONS
SS6638-27
SS6638-30
Output Voltage
SS6638-33
SS6638-50
Input Voltage
Start-Up Voltage
Min. Hold-on Voltage
No-Load Input Current
V
IN
=1.8V
V
IN
=1.8V
V
IN
=2.0V
V
IN
=3.0V
V
IN
V
START
V
HOLD
I
IN
15
42
50
60
I
DD1
90
µA
0.8
V
OUT
SYMBOL
MIN.
2.633
2.925
3.218
4.875
TYP.
2.700
3.000
3.300
5.000
MAX.
2.767
3.075
3.382
5.125
8
0.9
0.7
UNIT
V
Normal Operation
I
OUT
=1mA, V
IN
:0→2V
I
OUT
=1mA, V
IN
:2→0V
I
OUT
=0mA
SS6638-27
SS6638-30
SS6638-33
SS6638-50
EXT at no load, V
IN
=V
OUT
x 0.95
Measurement of the IC input
current (VOUT pin)
SS6638-27
SS6638-30
SS6638-33
V
V
V
µA
Supply Current
7
7
7
I
DD2
7
µA
Supply Current
SS6638-50
V
IN
=V
OUT
+ 0.5V
Measurement of the IC input
current (VOUT pin)
SW Leakage Current
V
S
W
=10V, V
IN
=V
OUT
+ 0.5V
SS6638-27
SS6638-30
1.3
1.2
R
ON
1.1
1
0.5
µA
SW Switch-On
Resistance
SS6638-33
SS6638-50
V
IN
=V
OUT
x 0.95, V
SW
=0.4V
V
IN
=V
OUT
x 0.95
Ω
Oscillator Duty Cycle
Measurement of the SW pin
waveform
V
IN
=V
OUT
x 0.95
DUTY
65
75
85
%
Max. Oscillator Freq.
Efficiency
Rev.2.01 6/26/2003
Measurement of the SW pin
waveform
F
OSC
η
80
105
85
130
KHz
%
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SS6638
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TYPICAL PERFORMANCE CHARACTERISTICS
(Refer to Typical Application)
Capacitor (C2): 47
µ
F (Tantalum Type)
Diode (D1):
1N5819 Schottky Type
2.8
85
80
2.7
Output Voltage (V)
V
IN
=1.5V
V
IN
=1.2V
2.5
Efficiency (%)
2.6
V
IN
=1.8V
V
IN
=
2.0V
75
70
V
IN
=1.8V
V
IN
=2.0V
2.4
65
V
IN
=0.9V
2.3
60
V
IN
=1.5V
V
IN
=0.9V
2.2
0
55
V
IN
=1.2V
40
60
80
100
120
140
160
180
20
40
60
80
100
120
140
160
180
0
20
Output Current (mA)
Fig. 1 SS6638-27 Load Regulation
(L=100
µ
H, CD54)
Output current (mA)
Fig. 2 SS6638-27 Efficiency (L=100µH, CD54)
2.8
85
80
2.7
75
Output Voltage (V)
2.6
Efficiency (%)
V
IN
=1.2V
2.5
V
IN
=1.5V
V
IN
=1.8V
V
IN
=2.0V
70
V
IN
=2.0V
65
60
V
IN
=1.8V
2.4
V
IN
=1.2V
55
V
IN
=1.5V
V
IN
=0.9V
V
IN
=0.9V
2.3
0
20
40
60
80
100
120
140
160
180
200
220
240
50
0
20
40
60
80
100
120
140
160
180
200
220 240
Output Current (mA)
Fig. 3
SS6638-27 Load Regulation (
L=47
µ
H, CD54)
Output current (mA)
Fig. 4 SS6638-27 Efficiency (L=47µH, CD54)
1.0
0.9
0.8
1.0
0.9
Start up
0.8
Start up
Input Voltage (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
2
4
6
8
10
12
14
16
18
Input Voltage (V)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
2
4
6
8
10
12
14
16
18
Hold on
Hold on
Output Current (mA)
Fig. 5 SS6638-27 Start-Up & Ho ld-ON Voltage (L=47µH, CD54)
Output Current (mA)
Fig. 6 SS6638-27
Start-Up & Ho ld-ON Voltage
(L=100µH, CD54)
CD54)
Rev.2.01 6/26/2003
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SS6638
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TYPICAL PERFORMANCE CHARACTERISTICS
(Continued)
2.78
2.76
2.74
2.72
2.70
2.68
2.66
2.64
2.62
-40
160
140
No Load
Switching Frequency (kHz)
Output Voltage V
OUT
(V)
120
100
80
60
40
20
-40
-20
0
20
40
60
80
100
-20
0
20
40
60
80
100
Fig. 7
Temperature (°C)
SS6638-27 Output Voltage vs. T emperature
Fig. 8
Temperature (
°
C)
SS6638-27 Switching Frequency vs . Temperature
82
80
1.8
1.6
Maximum Duty Cycle (%)
SW Turn On Resistance (Ω)
-20
0
20
40
60
80
100
78
76
74
72
70
68
66
-40
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-40
-20
0
Temperature (°C)
Fig. 9 SS6638-27 Maximum Duty Cycle vs. Temperature
Temperature (
°
C)
20
40
60
80
100
Fig. 10 SS6638-27 SW Turn On Resistance vs. Temperature
52
48
44
40
36
32
28
24
20
-40
3.1
3.0
2.9
V
IN
=2.0V
V
IN
=1.8V
Supply Current I
DD1
(µA)
Output voltage V
OUT
(V)
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
V
IN
=1.5V
V
IN
=1.2V
V
IN
=0.9V
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140
-20
0
20
40
60
80
100
Temperature (°C)
Fig. 11 SS6638-27 Supply Current vs. Temperature
Output Current (mA)
Fig.12 SS6638-30 Load Regulation (L=100µH, CD54)
Rev.2.01 6/26/2003
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