SS6638G
Simple
3-Pin Step-Up DC/DC Converter
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:
2.7V, 3.0V, 3.3V, 4.5V
and 5V.
Space
saving packages:
SOT-23, SOT-89
and TO-92.
DESCRIPTION
The
SS6638G
is a high-efficiency step-up DC/DC
converter for applications using 1 to 4 NiMH
battery cells. Only three external components are
required to deliver a fixed output voltage of 2.7V,
3.0V, 3.3V, 4.5V or 5V. The
SS6638G
starts up
from less than 0.9V input with 1mA load.
A
Pulse
Frequency Modulation scheme brings optimized
performance for applications with light output
loading and low input voltages. The output ripple
and noise are lower compared with circuits
operating in PSM mode.
The PFM control circuit operating
at a maximum
100kHz
switching rate results in smaller passive
components. The space saving SOT-23, SOT-89
and TO-92 packages make the
SS6638G
an ideal
choice of DC/DC converter for space-conscious
applications, like pagers, electronic cameras, and
wireless microphones.
Pb-free, RoHS compliant.
APPLICATIONS
Pagers.
Cameras.
Wireless Microphones.
Pocket Organizers.
Battery Backup Supplies.
Portable Instruments.
TYPICAL APPLICATION CIRCUIT
V
IN
L1
100µH
D1
SS12
SS6638-27G
SS6638-30G
SS6638-33G
SS6638-45G
SS6638-50G
GND
V
OUT
+
C1
SW
22µF
VOUT
+ C2
47µF
Simple
Step-Up DC/DC Converter
8/21/2005 Rev.2.3
www.SiliconStandard.com
1 of 19
SS6638G
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VOUT pin)
SW pin Voltage
SW pin Switch Current
Operating Temperature Range
Maximum Junction Temperature
Storage Temperature Range
Lead Temperature (Soldering 10 Sec.)
.6V
6V
0.6A
-40°C to 85°C
125°C
-65°C to 150
°C
260°C
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TEST CIRCUIT
I
IN
V
IN
D1
SS12
SS6638-27G
SS6638-30G
SS6638-33G
SS6638-45G
VOUT
SS6638-50G
GND
V
OUT
L1
100µH
+
C1
SW
22µF
+ C2
47µF
Fig. 1 Test Circuit 1
IS
SS6638G
VOUT
GND
SW
VSW
V
S
SS6638G
100
VOUT
GND
SW
F
OSC
VS
Fig. 2 Test Circuit 2
Fig. 3 Test Circuit 3
8/21/2005 Rev.2.3
www.SiliconStandard.com
3 of 19
SS6638G
ELECTRICAL CHARACTERISTICS
PARAMETER
(Continued)
TEST
CKT
TEST CONDITIONS
V
S
=V
OUT
x 0.95
SYMBOL
MIN.
TYP.
MAX.
UNIT
Oscillator Duty Cycle
Measurement of the SW
pin waveform
V
S
=V
OUT
x 0.95
3
DUTY
65
75
85
%
Max. Oscillator Freq.
Efficiency
Measurement of the SW
pin waveform
3
1
F
OSC
η
80
105
85
130
kHz
%
Note 1:
Specifications are production tested at T
A
=25°C. Specifications over the -40°C to 85°C operating
temperature range are assured by design, characterization and correlation with Statistical Quality
Controls (SQC).
TYPICAL PERFORMANCE CHARACTERISTICS
(Refer to Typical Application)
Capacitor (C2) : 47µF (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. 4 SS6638-27G Load Regulation
(L=100µH CD54)
Output current (mA)
Fig. 5 SS6638-27G 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. 6
SS6638-27G Load Regulation (
L=47µH CD54)
Output current (mA)
Fig. 7 SS6638-27G Efficiency (L=47µH CD54)
8/21/2005 Rev.2.3
www.SiliconStandard.com
5 of 19
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