Final
Impala Linear Corporation
ILC6380/1
SOT-89 Step-up Dual-Mode Switcher with Shutdown
General Description
100 mA boost convertor in 5-lead SOT-89 package
using both PFM and PWM conversion techniques. In
normal operation the ILC6380 runs in PWM mode run-
ning at one of three fixed frequencies. At light loads
the ILC6380 senses when the duty cycle drops to
approximately 10%, and automatically switches into a
power-saving PFM switching technique. This main-
tains high efficiencies both at full load and in system
sleep conditions.
Only 3 external components are needed to complete
the switcher design, and standard voltage options of
2.5, 3.3, and 5.0V at ±2.5% accuracy feature on-chip
phase compensation and soft-start design.
ILC6381 drives an external transistor for higher cur-
rent switcher design, with all of the features and bene-
fits of the ILC6380
Features
u
u
u
u
u
u
u
July 1996
85% efficiency at 50mA
Start-up voltages as low as 900mV
±2.5% accurate outputs
Complete switcher design with only 3 external
components
50, 100 and 180KHz switching frequency versions
available
Shutdown to 0.5µA Iq
External transistor option allows several hundred-
milliamp switcher design
Applications
u
u
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Cellular Phones, Pagers
Portable Cameras and Video Recorders
Palmtops and PDAs
Ordering Information*
Block Diagram
ILC6380CP-25
ILC6380CP-33
L
X
V
LX
LIMITER
BUFFER
Slow Start
2.5V±2.5%@50kHz
3.3V±2.5%@50kHz
5.0V±2.5%@50kHz
2.5V±2.5%@100kHz
3.3V±2.5%@100kHz
5.0V±2.5%@100kHz
2.5V±2.5%@180kHz
3.3V±2.5%@180kHz
5.0V±2.5%@180kHz
2.5V±2.5%@50kHz, external xtor
3.3V±2.5%@50kHz, external xtor
5.0V±2.5%@50kHz, external xtor
2.5V±2.5%@100kHz, external xtor
3.3V±2.5%@100kHz, external xtor
5.0V±2.5%@100kHz, external xtor
2.5V±2.5%@180kHz, external xtor
3.3V±2.5%@180kHz, external xtor
5.0V±2.5%@180kHz, external xtor
V
DD
V
OUT
ILC6380CP-50
ILC6380BP-25
ILC6380BP-33
ILC6380BP-50
ILC6380AP-25
ILC6380AP-33
ILC6380AP-50
ILC6381CP-25
ILC6381CP-33
ILC6381CP-50
V
SS
PWM/PFM Controlled
OSC
50/100/180KHz
V
ref
Phase comp
EXT
CE
-
CHIP ENABLE
+
V
DD
is internally connected to the V
OUT
pin.
Pin-Package Configurations
V
SS
5
L
X
4
V
SS
5
EXT
4
ILC6381BP-25
ILC6381BP-33
ILC6381BP-50
ILC6381AP-25
ILC6381AP-33
ILC6381AP-50
SOT -89-5
(TOP VIEW)
1
2
3
SOT -89-5
(TOP VIEW)
1
2
3
N/C
V
OUT
CE
N/C
V
OUT
CE
ILC6380
ILC6381
Impala Linear Corporation
* Standard product offering comes in tape & reel, quantity 1000
per reel, orientation right for SOT-89.
1
Electrical Characteristics ILC6380BP-50
V
OUT
=5.0V, F
OSC
=100kHz T
A
=25°C, Unless otherwise specified, V
IN
=V
OUT
X0.6, I
OUT
=50mA. See the schematic, Fig.1.
Parameter
CE “Low” Voltage
Symbol
V
CEL
I
CEH
I
CEL
V
LXLMT
Conditions
L
x
=10kΩ pull-up to 5V, V
OUT
=4.5V,
Stopped L
x
Oscillation
L
x
=10kΩ pull-up to 5V, V
OUT
=V
CE
=4.5V
L
x
=10kΩ pull-up to 5V, V
OUT
=4.5V, V
CE
=0V
L
x
=10kΩ pull-up to 5V, V
OUT
=4.5V, F
OSC
>
F
OSC
x 2
(3)
Min
Typ
Max
0.20
0.25
-0.25
Units
V
µA
µA
V
CE “High” Current
CE “Low” Current
L
x
Limit Voltage
0.7
1.1
Efficiency
Slow Start Time
Notes:
EFFI
Tss
85
10
%
msec
1. The Schottky diode (S.D.), in figure 1 must be type MA735, with Reverse current (I
R
) < 1.0µA at reverse voltage (V
R
)=10.0V
2. “Supply Current 1” is the supply current while the oscillator is continuously oscillating. In actual operation the oscillato
r periodically operates which results in less average power consumption.
The current that is actually provided by external V
IN
source is represented by “No-Load Input Current(I
IN
)”
3. Switching frequency is determined by delay time of internal comparator to turn Lx “off”, and minimum “on” time as determined
by MAXDTY spec.
Electrical Characteristics ILC6381BP-50
V
OUT
=5.0V, F
OSC
=100kHz T
A
=25°C, Unless otherwise specified, V
IN
=V
OUT
X0.6, I
OUT
=50mA. See the schematic, Fig.2.
Parameter
Output Voltage
Input Voltage
Oscillation Startup Voltage
Operation Startup Voltage
Supply Current 1
(2)
Supply Current 2
EXT “High” On Resistance
Symbol
V
OUT
V
IN
V
ST2
V
ST1
I
DD
1
I
DD
2
R
EXTH
R
EXTL
F
OSC
MAXDTY
Vout = V
ST2
Iout = 1mA
Conditions
Test Circuit of Figure 2
Min
4.875
Typ
5.000
Max
5.125
10
0.8
0.9
Units
V
V
V
V
µA
µA
Ω
Ω
kHz
%
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V
EXT=10kΩ pull-up to 5V, V
OUT
=5.5V
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V,
V
EXT
=V
OUT
-0.4V
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V,
V
EXT
=0.4V
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V, Mea-
suring of EXT waveform
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V, Mea-
suring of EXT high state
85
80
78.6
6.9
30
30
100
87
131.1
13.8
50
50
115
92
EXT “Low” On Resistance
Oscillator Frequency
Maximum Duty Ratio
Impala Linear Corporation
3
Electrical Characteristics ILC6381BP-50
V
OUT
=5.0V, F
OSC
=100kHz T
A
=25°C, Unless otherwise specified, V
IN
=V
OUT
X0.6, I
OUT
=50mA. See the schematic, Fig.2.
Parameter
CE “High”Voltage
CE “Low”Voltage
CE “High” Current
CE “Low” Current
Efficiency
Slow Start Time
Symbol
V
CEH
V
CEL
I
CEH
I
CEL
EFFI
T
SS
Conditions
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V, Ex-
istence of EXT oscillation
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V,
Stopped EXT oscillation
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V, V
CE
=V
OUT
X0.95V
EXT=10kΩ pull-up to 5V, V
OUT
=4.5V, V
CE
=0V
Min
0.75
Typ
Max
Units
V
0.10
0.25
-0.25
85
10
V
µA
µA
%
msec
Notes:
1. The Schottky diode (S.D.), in figure 1 must be type MA735, with Reverse current (I
R
) < 1.0µA at reverse voltage (V
R
)=10.0V
2. “Supply Current 1” is the supply current while the oscillator is continuously oscillating. In actual operation the oscillator
periodically operates which results in less average power consumption.
The current that is actually provided by external V
IN
source is represented by “No-Load Input Current(I
IN
)”
Applications Circuits
CE
SD
V
OUT
L
3
2
1
CE
V
OUT
L
V
IN
SD
3
2
1
ILC6380
V
IN
4
5
+
C
L
Tr
C
B
4
ILC6381
5
+
C
L
R
B
GND
GND
L:
100µH ( SUMIDA, CD-54)
L:
47µH ( SUMIDA, CD-54)
SD: Diode (Schottky diode; MATSUSHITA MA735)
C
L
: 16V 47µF (Tantalum Capacitor; NICHICON, F93)
SD: Diode (Schottky diode; MATSUSHITA MA735)
C
L
: 16V 47µF (Tantalum Capacitor; NICHICON, F93)
R
B
: 1kΩ
C
B
: 3300pF
Tr: 2SC3279, 2SDI628G
Fig. 1
ILC6380 Typical Application
Fig. 2
ILC6381 Typical Application
Impala Linear Corporation
4
Functions and Operation
The ILC6380 performs boost DC-DC conversion by control-
ling the switch element shown in the circuit below.
Dual Mode Operation
But there are downsides of PWM approaches, especially at
very low currents. Because the PWM technique relies on
constant switching and varying duty cycle to match the
load conditions, there is some point where the load current
gets too small to be handled efficiently. An actual switch
consumes some finite amount of current to switch on and
off; at very low currents this can be of the same magnitude
as the load current itself, driving switching efficiencies
down to 50% and below. The ILC6380 and ILC6381 over-
come this limitation by automatically switching over to a
PFM, or Pulse Frequency Modulation, technique at low
currents. This technique conserves power loss by only
switching the output if the current drain requires it. As
shown in the diagram below, the waveform actually skips
pulses depending on the power needed by the output.
[This
technique is also called “pulse skipping” because of
this characteristic.]
When the switch is closed, current is built up through the
inductor. When the switch opens, this current has to go
somewhere and is forced through the diode to the output. As
this on and off switching continues, the output capacitor volt-
age builds up due to the charge it is storing from the inductor
current. In this way, the output voltage gets boosted relative
to the input. The ILC6380 monitors the voltage on the output
capacitor to determine how much and how often to drive the
switch.
In general, the switching characteristic is determined by the
output voltage desired and the current required by the load.
Specifically the energy transfer is determined by the power
stored in the coil during each switching cycle.
P
L
= ƒ(t
ON
, V
IN
)
The ILC6380 and ILC6381 use a PWM or Pulse Width Mod-
ulation technique. The parts come in one of three fixed inter-
nal frequencies: 50, 100, or 180kHz. The switches are
constantly driven at these frequencies. The control circuitry
varies the power being delivered to the load by varying the
on-time, or duty cycle, of the switch. Since more on-time
translates to higher current build-up in the inductor, the max-
imum duty cycle of the switch determines the maximum load
current that the device can support. The ILC6380 and
ILC6381 both support up to 87% duty cycles, for maximum
usable range of load currents.
There are two key advantages of the PWM type controllers.
First, because the controller automatically varies the duty
cycle of the switch’s on-time in response to changing load
conditions, the PWM controller will always have an opti-
mized waveform for a steady-state load. This translates to
very good efficiency at high currents and minimal ripple on
the output. [Ripple
is due to the output cap constantly
accepting and storing the charge received from the inductor,
and delivering charge as required by the load. The “pump-
ing” action of the switch produces a sawtooth-shaped volt-
age as seen by the output.]
The other key advantage of the PWM type controllers is that
the radiated noise due to the switching transients will always
occur at the (fixed) switching frequency. Many applications
do not care much about switching noise, but certain type of
applications, especially communication equipment, need to
minimize the high frequency interference within their system
as much as is possible. Using a boost converter requires a
certain amount of higher frequency noise to be generated;
using a PWM converter makes that noise highly predictable,
and thus easier to filter out.
Switch Waveform
V
SET
V
OUT
In the ILC6380 and ILC6381, this switchover is internally
set to be at the point where the PWM waveform hits
approximately 10% duty cycle. So the PFM mode is run-
ning at 10% duty cycle at the rated frequency; for 100kHz
part this means a constant on-time of 1µsec. This not only
is ideal for efficiency at these low currents, but a 10% duty
cycle will have much better output ripple characteristics
than a similarly configured PFM part, such as the ILC6390
and ILC6391.
The Dual-Mode architecture was designed specifically for
those applications, like communications, which need the
spectral predictability of a PWM-type DC-DC converter, yet
which also needs the highest efficiencies possible, espe-
cially in Shutdown or Standby mode.
[For other conversion
techniques, please see the ILC6370/71 and ILC6390/91
datasheets.]
Other Considerations
The other limitation of PWM techniques is that, while the
fundamental switching frequency is easier to filter out since
it’s constant, the higher order harmonics of PWM will be
present and may have to be filtered out, as well. Any filter-
ing requirements, though, will vary by application and by
actual system design and layout, so generalizations in this
area are difficult, at best.
However, PWM control for boost DC-DC conversion is
widely used, especially in audio-noise sensitive applica-
tions or applications requiring strict filtering of the high fre-
quency components. Impala’s products give very good
Impala Linear Corporation
5
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