SM6702 series
NIPPON PRECISION CIRCUITS INC.
PFM Step-up DC/DC Converter
OVERVIEW
The SM6702 series are step-up DC/DC converter ICs, fabricated using NPC’s Molybdenum-gate CMOS pro-
cess. They incorporate reference voltage source, error amplifier, oscillator, start-up circuit, PFM (Pulse Fre-
quency Modulation) control circuit into a single chip. The only external components required are a Coil, Diode
and output smoothing capacitors to form a step-up DC/DC converter. They employ PFM voltage control cir-
cuits to achieve high efficiency, stable constant-voltage output.
FEATURES
I
I
I
I
I
I
Power dissipation : 24
µW
at V
IN
= 1.5 V, V
OUT
= 3.0 V, I
OUT
= 100
µA
Start-up input voltage : 0.9 V (max) at R
L
= 30 kΩ
Output voltage : 2.2 V to 3.3 V, available in 0.1 Vstep
High efficiency : 85% at V
IN
= 1.5 V, V
OUT
= 3.0 V, I
OUT
= 1 mA
Low ripple voltage
Package : SOT23-3, SOT89-3
APPLICATIONS
I
I
I
I
I
PDA, Mobile IT equipment
Digital Stil Camera
Pager
Constant-voltage sources for battery-operated equipment
Local voltage sources
ORDERING INFORMATION
D e vice
SM6702-33HB
SM6702-30HA
SM6702-30HB
SM6702-27HA
SM6702-27HB
SM6702-24HA
Output voltag e
1
3.3 V
3.0 V
3.0 V
2.7 V
2.7 V
2.4 V
P ackag e
S O T89-3
S O T23-3
S O T89-3
S O T23-3
S O T89-3
S O T23-3
1. Stepwise setting with a step of 0.1V in the range of 2.2V to 3.3V is available.
NIPPON PRECISION CIRCUITS—1
SM6702 series
PINOUT
(Top view)
SM6702−××HA(SOT23−3)
SM6702−××HB(SOT89−3)
3
2
1
2
0 2
1
2
3
PIN DESCRIPTION
Number
S M 6 7 0 2
−××H
A
1
2
3
S M 6 7 0 2
−××H
B
1
3
2
Name
VSS
LX
OUT
Ground
Switching pin
Output (device supply pin)
Description
PACKAGE DIMENSIONS
(Unit : mm)
SM6702−××HA(SOT23−3)
SM6702−××HB(SOT89−3)
4.5
±
0.1
1.5
±
0.1
0.4
±
0.1
(5 )
4.0
±
0.3
0.1
±
0.05
(8 )
0.42
±
0.1
(5 )
0.37
±
0.1
2.9
±
0.2
0 to 15
(0.4)
1.55
±
0.15
0.2min
1.6
±
0.2
2.8
±
0.2
1.1
±
0.2
0.95 0.95
0.8
±
0.1
1.1
±
0.2
0.15
±
0.1
2.5
±
0.1
φ
1
.0
1.5
1.5
(8 )
0.4
±
0.1
0.2
M
0.05
±
0.05
0.42
±
0.1
0.47
±
0.1
NIPPON PRECISION CIRCUITS—2
SM6702 series
BLOCK DIAGRAM
OUT
LX
PFM OSC
VREF
START−UP
VSS
NIPPON PRECISION CIRCUITS—3
SM6702 series
SPECIFICATIONS
Absolute Maximum Ratings
T
a
= 25
°C
P arameter
LX impressed voltage
OUT impressed voltage
LX output current
Pow er dissipation
Operating temperature
Storage temperature
Symbol
V
LX
V
OUT
I
L X
P
D
T
opr
T
stg
S M 6 7 0 2
−××H
A
S M 6 7 0 2
−××H
B
Condition
Rating
5
4
200
150
mW
500
−
20 to 70
−
40 to 125
°C
°C
Unit
V
V
mA
Electrical Characteristics
L = 330 µH, C = 22 µF, T
a
= 25
°C,
V
SS
= 0 V
Rating
P arameter
Start-up voltage
Holding voltage
Current consumption
Output voltage
Symbol
V
st
V
hold
I
S S
V
OUT
I
L X
I
L X L
f
O S C
Duty
V
IN
R
L
= 30 kΩ
R
L
= 3 kΩ
V
IN
= 1.5 V, R
L
= 30 kΩ
V
IN
= 1.5 V, R
L
= 3 kΩ
V
O U T
= V
target
−
0.1,
V
L X
= 0.4 V
V
O U T
= V
L X
= 3.5 V
V
O U T
= V
target
−
0.1
V
O U T
= V
target
−
0.1
2.2
≤
V
target
≤
2.7
2.8
≤
V
target
≤
3.3
Condition
min
–
–
–
V
target
×
0.975
60
80
–
80
65
–
typ
–
–
8
V
target
–
–
–
100
75
–
max
0.9
0.7
16
V
target
×
1.025
–
mA
–
1
120
85
V
target
+
0.2
µA
kHz
%
V
V
V
µA
V
Unit
LX output current
LX leakage current
M a x i m um oscillator frequency
Switch ON duty cycle
Input voltage range
V
target
: Setting output voltage
NIPPON PRECISION CIRCUITS—4
SM6702 series
FUNCTIONAL DESCRIPTION
Step-up Principle
The SM6702 series use a transistor to switch the input supply in a non-isolated chopper switching regulator
configuration. The figure below shows the basic step-up switching regulator circuit.
If the transistor is ON for an interval t
ON
and then instantly turned OFF, the energy stored in the coil L during
the interval t
ON
generates a voltage V
L
across the coil. This voltage is superimposed on the input voltage such
that the peak voltage reaches V
IN
+ V
L
which forces the diode D to conduct and release the stored energy into
the output.
During normal operation, the above switching occurs repeatedly at a frequency controlled by an oscillator
(which can change depending on the input and output load conditions), generating a square wave output which
is then smoothed by the output capacitor C. Thus the output voltage (V
OUT
> V
IN
) has been stepped up.
L
V
IN
D
V
OUT
Tr
C
GND
PFM Control
In SM6702 series, the LX transistor ON interval is fixed, and the OFF interval varies in response to the input
voltage and load changes. Thus the resulting switching cycle frequency varies, called pulse frequency modula-
tion.
NIPPON PRECISION CIRCUITS—5
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