ADP1108AN-5-ADP1108AR-ADP1108AR-12-ADP1108AR-3.3-ADP1108AR-5 Fast Delivery |IC PHOENIX CO.,LIMITED

ADP1108AR ,Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 VGENERAL DESCRIPTION GAIN BLOCK/LIMERROR AMPThe ADP1108 is a highly versatile micropower switch-mode ..
ADP1108AR ,Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 VAPPLICATIONSCOMPARATORDRIVERNotebook/Palm Top Computers3 V to 5 V, 5 V to 12 V ConvertersSW2GND FB9 ..
ADP1108AR-12 ,Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 VFEATURES FUNCTIONAL BLOCK DIAGRAMSOperates at Supply Voltages From 2.0 V to 30 VConsumes Only 110 m ..
ADP1108AR-3.3 ,Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 VMicropower DC-DC ConverteraAdjustable and Fixed 3.3 V, 5 V, 12 VADP1108
ADP1108AR-5 ,Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 VSpecifications subject to change without notice.–2– REV. 0ADP1108ABSOLUTE MAXIMUM RATINGS* PIN CONF ..
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ADP1108AN-5-ADP1108AR-ADP1108AR-12-ADP1108AR-3.3-ADP1108AR-5
Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
REV.0Micropower DC-DC Converter
Adjustable and Fixed 3.3 V, 5 V, 12 V
FUNCTIONAL BLOCK DIAGRAMS
SET
VIN
SW2FBGND
SW1
ILIM
SET
VINSW2
SENSEGND
SW1
ILIM
GENERAL DESCRIPTION
The ADP1108 is a highly versatile micropower switch-mode
dc-dc converter that operates from an input voltage supply as
low as 2.0 V and typically starts up from 1.8 V.
The ADP1108 can be programmed into a step-up or step-down
dc-to-dc converter with only three external components. The
fixed outputs are 3.3 V, 5 V and 12 V. An adjustable version is
also available. In step-up mode, supply voltage range is 2.0 V to
12 V, and 30 V in step-down mode. The ADP1108 can deliver
150 mA at 5 V from a 2 AA cell input and 300mA at 5 V from
a 9 V input in step-down mode. Switch current limit can be
programmed with a single resistor.
For battery operated and power conscious applications, the
ADP1108 offers a very low power consumption of less than
110μA.
The auxiliary gain block available in ADP1108 can be used
as a low battery detector, linear post regulator, under voltage
lockout circuit or error amplifier.
FEATURES
Operates at Supply Voltages From 2.0 V to 30 V
Consumes Only 110 mA Supply Current
Step-Up or Step-Down Mode Operation
Minimum External Components Required
Low Battery Detector Comparator On-Chip
User-Adjustable Current Limit
Internal 1 A Power Switch
Fixed or Adjustable Output Voltage Versions
8-Pin DIP or SO-8 Package
APPLICATIONS
Notebook/Palm Top Computers
3 V to 5 V, 5 V to 12 V Converters
9 V to 5 V, 12 V to 5 V Converters
LCD Bias Generators
Peripherals and Add-On Cards
Battery Backup Supplies
Cellular Telephones
Portable Instruments
ADP1108–SPECIFICATIONS
OUTPUT SENSE VOLTAGE
CURRENT LIMIT
NOTESThis specification guarantees that both the high and low trip points of the comparator fall within the 1.20 V to 1.30 V range.The output voltage waveform will exhibit a sawtooth shape due to the comparator hysteresis. The output voltage on the fixed output versions will always be within the
specified range.100 kΩ resistor connected between a 5 V source and the AO pin.
All limits at temperature extremes are guaranteed via correlation using standard Quality Control methods.
(08C to +708C, VIN = 3.0 V unless otherwise noted)
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . .+36 V
SW1 Pin Voltage (VSW1) . . . . . . . . . . . . . . . . . . . . . . . .+50 V
SW2 Pin Voltage (VSW2) . . . . . . . . . . . . . . . . . .–0.5 V to VIN
Feedback Pin Voltage (ADP1108) . . . . . . . . . . . . . . . .+5.5 V
Sense Pin Voltage (ADP1108, 3.3, 5, 12) . . . . . . . . . . .+36 V
Maximum Power Dissipation . . . . . . . . . . . . . . . . . .500 mW
Maximum Switch Current . . . . . . . . . . . . . . . . . . . . . . . .1.5 A
Operating Temperature Range . . . . . . . . . . . . .0°C to 170°C
Storage Temperature Range . . . . . . . . . . . .–65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . .+300°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
ORDERING GUIDE
*N = Plastic DIP, SO = Small Outline Package.
PIN CONFIGURATIONS
8-Lead Plastic DIP 8-Lead SOIC
(N-8) (SO-8)
ILIM
VIN
SW1
SW2
FB (SENSE)*
SET
GND
* FIXED VERSIONS
ILIM
VIN
SW1
SW2
FB (SENSE)*
SET
GND
* FIXED VERSIONS
PIN FUNCTION DESCRIPTIONS
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADP1108 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
ADP1108
–Typical Performance Characteristics
SWITCH CURRENT – Amps
(SAT)
– Volts
Figure 1. Saturation Voltage vs. ISWITCH
Current in Step-Up Mode
RLIM – Ω
SWITCH CURRENT – mA
11001k
100
Figure 4. Maximum Switch Current
vs. RLIM In Step-Down Mode
TEMPERATURE – °C
OSCILLATOR FREQUENCY – kHz–400852570
Figure 7. Oscillator Frequency vs.
Temperature
SWITCH CURRENT – Amps
SWITCH ON VOLTAGE – Volts
0.05
Figure 2. Switch ON Voltage vs.
Switch Current In Step-Down Mode
SWITCH CURRENT – mA
SUPPLY CURRENT – mA
1000100900200300400600700800500
Figure 5. Supply Current vs. Switch
Current
TEMPERATURE – °C–400852570
DUTY CYCLE – %
Figure 8. Duty Cycle vs. Temperature
RLIM – Ω
SWITCH CURRENT – mA
100101001k
200
Figure 3. Maximum Switch Current
vs. RLIM In Step-Up Mode
TEMPERATURE – °C
QUIESCENT CURRENT – µA
100
Figure 6. Quiescent Current vs.
Temperature
TEMPERATURE – °C
SWITCH ON TIME – µs
32.5
Figure 9. Switch ON Time vs.
Temperature
THEORY OF OPERATION
The ADP1108 is a flexible, low power Switch Mode Power
Supply (SMPS) controller. The regulated output voltage can be
greater than the input voltage (boost or step-up mode) or less
than the input (buck or step-down mode). This device uses a
gated-oscillator technique to provide very high performance
with low quiescent current.
A functional block diagram of the ADP1108 is shown on
the front page. The internal 1.245 V reference is connected to
one input of the comparator, while the other input is externally
connected (via the FB pin) to a feedback network connected to
the regulated output. When the voltage at the FB pin falls
below 1.245 V, the 19 kHz oscillator turns on. A driver amplifier
provides base drive to the internal power switch, and the switching
action raises the output voltage. When the voltage at the FB pin
exceeds 1.245 V, the oscillator is shut off. While the oscillator is
off, the ADP1108 quiescent current is only 110 μA. The
comparator includes a small amount of hysteresis, which
ensures loop stability without requiring external components
for frequency compensation.
The maximum current in the internal power switch can be set
by connecting a resistor between VIN and the ILIM pin. When
the maximum current is exceeded, the switch is turned OFF.
The current limit circuitry has a time delay of about 2 μs. If
an external resistor is not used, connect ILIM to VIN. Further
information on ILIM is included in the Limiting the Switch
Current section of this data sheet.
The ADP1108 internal oscillator provides 36 μs ON and 17 μs
OFF times, which is ideal for applications where the ratio
between VIN and VOUT is roughly a factor of three (such as
generating +5 V from a +2 V input). The 36 μs/17 μs ratio
permits continuous mode operation in such cases, which
increases the available output power.
An uncommitted gain block on the ADP1108 can be connected
as a low-battery detector. The inverting input of the gain block
is internally connected to the 1.245 V reference. The noninverting
input is available at the SET pin. A resistor divider, connected
between VIN and GND with the junction connected to the SET
pin, causes the AO output to go LOW when the low battery set
The ADP1108 provides external connections for both the collector
and emitter of its internal power switch, which permits both
step-up and step-down modes of operation. For the step-up mode,
the emitter (Pin SW2) is connected to GND and the collector
(Pin SW1) drives the inductor. For step-down mode, the emitter
drives the inductor while the collector is connected to VIN.
The output voltage of the ADP1108 is set with two external
resistors. Three fixed-voltage models are also available: ADP1108-
3.3 (+3.3 V), ADP1108-5 (+5 V) and ADP1108-12 (+12 V). The
fixed-voltage models are identical to the ADP1108, except that
laser-trimmed voltage-setting resistors are included on the chip.
On the fixed-voltage models of the ADP1108, simply connect
the feedback pin (Pin 8) directly to the output voltage.
COMPONENT SELECTION
General Notes on Inductor Selection
When the ADP1108 internal power switch turns on, current
begins to flow in the inductor. Energy is stored in the inductor
core while the switch is on, and this stored energy is then
transferred to the load when the switch turns off. Both the
collector and the emitter of the switch transistor are accessible
on the ADP1108, so the output voltage can be higher, lower, or
of opposite polarity than the input voltage.
To specify an inductor for the ADP1108, the proper values of
inductance, saturation current, and dc resistance must be
determined. This process is not difficult, and specific equations
for each circuit configuration are provided in this data sheet. In
general terms, however, the inductance value must be low
enough to store the required amount of energy (when both
input voltage and switch ON time are at a minimum) but high
enough that the inductor will not saturate when both VIN and
switch ON time are at their maximum values. The inductor
must also store enough energy to supply the load, without
saturating. Finally, the dc resistance of the inductor should be
low, so that excessive power will not be wasted by heating the
windings. For most ADP1108 applications, an inductor of
47 μH to 330 μH, with a saturation current rating of 300 mA to
1 A and dc resistance < 0.4 V is suitable. Ferrite core inductors
that meet these specifications are available in small, surface-
mount packages.
TEMPERATURE – °C
CE (SAT)
– Volts
0.33
Figure 10.Switch Saturation Voltage In
Step-Up Mode vs. Temperature
TEMPERATURE – °C
CE (SAT)
– Volts
0.95
Figure 11.Switch Saturation Voltage In
Step-Down Mode vs. Temperature
ADP1108
Calculating the Inductor Value
Selecting the proper inductor value is a simple three-step
process:
1. Define the operating parameters: minimum input voltage,
maximum input voltage, output voltage and output current.
2. Select the appropriate conversion topology (step-up, step-
down or inverting).
3. Calculate the inductor value, using the equations in the fol-
lowing sections.
Inductor Selection—Step-Up Converter
In a step-up or boost converter (Figure 15), the inductor must
store enough power to make up the difference between the input
voltage and the output voltage. The inductor power is calculated
from the equation:PL=VOUT+VD−VINMIN()()×IOUT()(Equation 1)
where VD is the diode forward voltage (≈ 0.5 V for a 1N5818
Schottky). Energy is only stored in the inductor while the
ADP1108 switch is ON, so the energy stored in the inductor on
each switching cycle must be equal to or greater than:OSC(Equation 2)
in order for the ADP1108 to regulate the output voltage.
When the internal power switch turns ON, current flow in the
inductor increases at the rate of: (t)=VIN1−e
±R©t(Equation 3)
where L is in henrys and R9 is the sum of the switch equivalent
resistance (typically 0.8 Ω at +25°C) and the dc resistance of
the inductor. If the voltage drop across the switch is small
compared to VIN, a simpler equation can be used:
IL(t)=VINt(Equation 4)
Replacing t in the above equation with the ON time of the
ADP1108 (36 μs, typical) will define the peak current for a
given inductor value and input voltage. At this point, the
inductor energy can be calculated as follows: =1L×I2PEAK(Equation 5)
As previously mentioned, EL must be greater than PL/fOSC so the
ADP1108 can deliver the necessary power to the load. For best
efficiency, peak current should be limited to 1 A or less. Higher
switch currents will reduce efficiency because of increased satura-
tion voltage in the switch. High peak current also increases output
ripple. As a general rule, keep peak current as low as possible to
minimize losses in the switch, inductor and diode.
In practice, the inductor value is easily selected using the equations
above. For example, consider a supply that will generate 12 V
at 30 mA from a 3 V battery, assuming a 2 V end-of-life voltage.
On each switching cycle, the inductor must supply:
fOSC=315mW
19kHz=16.6μJ
The required inductor power is fairly low in this example, so the
peak current can also be low. Assuming a peak current of
500 mA as a starting point, Equation 4 can be rearranged to
recommend an inductor value: =VINL(MAX)=2V
500mA36μs=144μH
Substituting a standard inductor value of 100 μH with 0.2 Ω dc
resistance, will produce a peak switch current of:
IPEAK=2V
1.0Ω1±e
±1.0Ω×36μs
100μH=605mA
Once the peak current is known, the inductor energy can be
calculated from Equation 5: =1100μH×605mA()=18.3μJ
The inductor energy of 18.3 μJ is greater than the PL/fOSC
requirement of 16.6 μJ, so the 100 μH inductor will work in this
application. By substituting other inductor values into the same
equations, the optimum inductor value can be selected. When
selecting an inductor, the peak current must not exceed the
maximum switch current of 1.5 A. If the calculated peak current
is greater than 1.5 A, either the ADP3000 should be considered
or an external power transistor can be used.
The peak current must be evaluated for both minimum and
maximum values of input voltage. If the switch current is high
when VIN is at its minimum, the 1.5 A limit may be exceeded at the
maximum value of VIN. In this case, the current limit feature of
the ADP1108 can be used to limit switch current. Simply select
a resistor (using Figure 3) that will limit the maximum switch
current to the IPEAK value calculated for the minimum value of
VIN. This will improve efficiency by producing a constant
IPEAK as VIN increases. See the Limiting the Switch Current
section of this data sheet for more information.
Note that the switch current limit feature does not protect the
circuit if the output is shorted to ground. In this case, current is
limited only by the dc resistance of the inductor and the forward
voltage of the diode.
Inductor Selection—Step-Down Converter
The step-down mode of operation is shown in Figure 16. Unlike
the step-up mode, the ADP1108’s power switch does not
saturate when operating in the step-down mode. Therefore,
switch current should be limited to 650 mA in this mode. If the
input voltage will vary over a wide range, the ILIM pin can be
used to limit the maximum switch current. Higher switch current
is possible by adding an external switching transistor, as shown
in Figure 18.

Partno	Mfg	Dc	Qty	Available	Descript
ADP1108AN-5 \|ADP1108AN5	ADI	N/a	5	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
ADP1108AR	ADI	N/a	2	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
ADP1108AR	AD	N/a	351	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
ADP1108AR-12 \|ADP1108AR12	AD	N/a	30	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
ADP1108AR-3.3 \|ADP1108AR33	ADI	N/a	8	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V
ADP1108AR-5 \|ADP1108AR5	AD	N/a	98	avai	Micropower DC-DC Converter Adjustable and Fixed 3.3 V, 5 V, 12 V