AIC AIC1638-27CX 3-pin one-cell step-up dc/dc converter Datasheet

AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
FEATURES
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DESCRIPTION
Guaranteed Start-Up from below 0.9 V.
High Efficiency.
Low Quiescent Current.
Few Number of External Components needed.
Low Ripple and Low Noise.
Fixed Output Voltage: 2.7V, 3.0V, 3.3V, and 5V.
Space Saving SOT-89 and TO-92 Packages.
The AIC1638 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, or
5V. The AIC1638 starts up from below 0.9V input with
1mA load. 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 the circuits
operating in PSM mode.
APPLICATIONS
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Pagers.
Cameras.
Wireless Microphones.
Pocket Organizers.
Battery Backup Suppliers.
Portable Instruments.
The PFM control circuit operating in 100KHz (max.)
switching rate results in smaller passive
components. The space saving SOT-89 and TO-92
packages make the AIC1638 an ideal choice of
DC/DC converter
for space conscious
applications, like pagers, electronic cameras, and
wireless microphones
TYPICAL APPLICATION CIRCUIT
VIN
+
C2
47µF
L1
88µH
D1
VOUT
SW
AIC1638-27
AIC1638-30
AIC1638-33
AIC1638-50
VOUT
+
GND
C1
22µF
One Cell Step-Up DC/DC Converter
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
www.analog.com.tw
TEL: (8863)577-2500 FAX:(8863)577-2510
1
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
ORDERING INFORMATION
AIC1638- XXX
ORDER NUMBER
AIC1638-27CX
AIC1638-30CX
AIC1638-33CX
AIC1638-50CX
(SOT-89)
PACKAGE TYPE
X: SOT-89
Z: TO-92
PIN CONFIGURATION
TOP VIEW
1: GND
2: VOUT
3: SW
TEMPERATURE RANGE
C: -20°C+80°C
1
OUTPUT VOLTAGE
27: 2.7V
30: 3.0V
33: 3.3V
50: 5.0V
AIC1638-27CZ
AIC1638-30CZ
AIC1638-33CZ
AIC1638-50CZ
(TO-92)
TOP VIEW
1: GND
2: VOUT
3: SW
2
3
1
2
3
ABSOLUATE MAXIMUM RATINGS
Supply Voltage
………………………………………………………………………….12V
SW pin Voltage ………………………………………….…………………………………….12V
SW pin Switch Current
Power Dissipation
……………………………………………………………………0.6A
……………………………………………………..……………….500mW
Operating Temperature Range ………………………………..…………….….-20°C to 80 °C
Storage Temperature Range ………………………………………………… -65°C to 150 °C
Lead Temperature (Sordering 10 Sec.)
…………………………………………………260°C
TEST CIRCUIT
AIC1638
2.5V
VOUT
100
FOUT
SW
GND
Oscillator Test Circuit
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
2
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage
(Ta=25°°C, IO=10mA, Unless otherwise specified)
SYMBOL
MIN.
TYP.
MAX.
UNIT
VOUT
2.633
2.700
2.767
V
VIN=1.8V
2.925
3.000
3.075
VIN=2.0V
3.218
3.300
3.382
VIN=3.0V
4.875
5.000
5.125
TEST CONDITIONS
VIN=1.8V
Input Voltage
VIN
Start-Up Voltage
IOUT=1mA, VIN:0→2V
VSTART
Min. Hold-on Voltage
IOUT=1mA, VIN:2→0V
VHOLD
No-Load Input Current
IOUT=0mA
Supply Current
VIN=VOUT x 0.95
0.8
8
V
0.9
V
0.7
V
IIN
15
µA
IDD1
42
µA
50
Measurement of the IC input
current
60
90
Supply Current
VIN=VOUT + 0.5V
7
IDD2
µA
Measurement of the IC input
current
SW Leakage Current
VSW =10V, VIN=VOUT + 0.5V
SW Switch-On
Resistance
VIN=VSW x 0.95, VSW =0.4V
0.5
1.3
RON
µA
Ω
1.2
1.1
1
Oscillator Duty Cycle
VIN=VOUT x 0.95
DUTY
65
75
85
%
FOSC
80
105
130
KHz
Measurement of the IC input
current
Max. Oscillator Freq.
VIN=VOUT x 0.95
Measurement of the IC input
current
Efficiency
η
85
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
%
3
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS
Capacitor (C1) : 47 µ F (Tantalum Type)
Diode
(D1) : 1N5819 Schottky Type
AIC1638-27 Load Regulation (L=100µH CD54)
80
2.7
2.6
VIN=1.8V
VIN=1.5V
75
VIN=2.0V
Efficiency (%)
Output voltage (V)
AIC1638-27 Efficiency (L=100µH CD54)
85
2.8
VIN=1.2V
2.5
2.4
VIN=1.8V
70
VIN=2.0V
65
VIN=1.5V
VIN=0.9V
60
2.3
VIN=1.2V
VIN=0.9V
55
2.2 0
20
40
60
80
100
120
140
160
0
180
20
40
60
80
100
120
140
160
180
Output current (mA)
Output Current (mA)
AIC1638-27 Efficiency
AIC1638-27 Load Regulation (L=47µH CD54)
(L=47µH CD54)
85
2.8
80
2.7
2.6
VIN=1.5V
VIN=1.2V
Efficiency (%)
Output voltage (V)
75
VIN=2.0V
VIN=1.8V
2.5
70
VIN=2.0V
VIN=1.8V
65
60
VIN=1.2V
2.4
VIN=1.5V
VIN=0.9V
55
VIN=0.9V
2.3
0
20
40
60
80
100
120
140
160
180
200
220
50
240
0
20
40
60
80
Output Current (mA)
1.0
0.9
0.9
Input Voltage (V)
Input Voltage (V)
0.7
0.6
0.5
Hold on
0.3
6
8
10
220 240
12
Output Current (mA)
14
16
18
0.3
0.0
Hold on
0.4
0.1
4
200
0.5
0.2
2
180
0.6
0.1
0
160
0.7
0.2
0.0
140
Start up
0.8
Start up
0.4
120
AIC1638-27 Start-Up & Hold-ON Voltage (L=100µH)
AIC1638-27 Start-Up & Hold-ON Voltage (L=47µH)
1.0
0.8
100
Output current (mA)
0
2
4
6
8
10
12
14
16
18
Output Current (mA)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
4
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
AIC1638-27 Output Voltage vs Temperature
AIC1638-27 Switching Frequency vs Temperature
2.78
160
140
Switching Frequency (kHz)
Output Voltage Vout (V)
2.76
No Load
2.74
2.72
2.70
2.68
2.66
120
100
80
60
40
2.64
2.62
-40
-20
0
20
40
60
80
20
-40
100
-20
0
20
Temperature (°C)
AIC1638-27 Maximum Duty Cycle vs Temperature
100
1.6
SW Turn On Resistance (Ω)
Maximum Duty Cycle (%)
80
AIC1638-27 SW On Resistance vs Temperature
80
78
76
74
72
70
68
-20
0
20
40
60
80
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-40
100
-20
0
20
Temperature (°C)
40
60
80
100
Temperature (°C)
µH, CD54)
AIC1638-30 Load Regulation (L=100µ
AIC1638-27 Supply Current vs Temperature
3.1
52
2.0V
3.0
48
2.9
Output voltage VOUT(V)
Supply Current IDD1 (uA)
60
1.8
82
66
-40
40
Temperature (°C)
44
40
36
32
28
1.8V
2.7
2.6
2.5
2.4
2.3
1.2V
2.2
VIN=0.9V
2.1
24
2.0
20
-40
1.5V
2.8
-20
0
20
40
60
80
100
Temperature (°C)
0
10
20
30
40
50
60
70
80
90
100 110 120 130 140
Output Current (mA)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
5
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
µH CD54)
AIC1638-30 Load Regulation (L=47µ
µH, CD54)
AIC1638-30 Efficiency (L=100µ
3.1
85
3.0
80
Output Voltage (V)
2.9
Efficiency (%)
75
70
2.0V
1.8V
65
60
50
0
20
60
2.4
2.2
80
100
120
140
160
VIN=0.9V
0
20
40
60
80
100
120
140
160
180
200
220
180
Output Current (mA)
Output Current (mA)
AIC1638-30 Start-up & Hold-on Voltage (L=100µH)
µH CD54)
AIC1638-30 Efficiency (L=47µ
85
VIN=2.0V
2.5
1.2V
40
VIN=1.8V
2.6
2.3
VIN=0.9V
VIN=1.5V
2.7
1.5V
55
VIN=1.2V
2.8
1.0
Start up
0.9
80
0.8
Input Voltage (V)
Efficiency (%)
75
70
65
VIN=2.0V
VIN=1.8V
60
55
VIN=1.5V
VIN=0.9V
50
0
50
75
0.6
Hold on
0.5
0.4
0.3
0.2
VIN=1.2V
25
0.7
0.1
100
125
150
175
200
225
0.0
0
Output Current (mA)
4
6
8
10
12
14
16
18
20
Output Current (mA)
AIC1638-30 Start-up & Hold-on Voltage (L=47uH)
AIC1638-30 Output Voltage vs Temperature
3.06
1.0
Start up
0.9
3.04
Output Voltage Vout (V)
0.8
Input Voltage (V)
2
0.7
0.6
0.5
Hold on
0.4
0.3
0.2
No Load
3.02
3.00
2.98
2.96
2.94
2.92
0.1
0.0
0
2
4
6
8
10
12
14
16
18
20
Output Current (mA)
2.90
-40
-20
0
20
40
60
80
100
Temperature (°C)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
6
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
AIC1638-30 Maximum Duty Cycle vs Temperature
82
140
80
Maximum Duty Cycle (%)
Switching Frequency (kHz)
AIC1638-30 Switching Frequency vs Temperature
160
120
100
80
60
40
78
76
74
72
70
68
20
0
-40
-20
0
20
40
60
80
66
-40
100
-20
0
1.8
52
1.6
48
Supply Current IDD1 (µA)
SW Turn On Resistance (Ω)
40
60
80
100
AIC1638-30 Supply Current vs Temperature
AIC1638-30 SW On Resistance vs Temperature
1.4
1.2
1.0
0.8
0.6
0.4
44
40
36
32
28
24
0.2
0.0
-40
20
Temperature (°C)
Temperature (°C)
-20
0
20
40
60
80
20
-40
100
-20
0
20
40
60
80
100
Temperature (°C)
Temperature (°C)
AIC1638-33 Load Regulation (L=100µH, CD54)
AIC1638-33 Efficiency (L=100µH, CD54)
90
3.4
VIN=2.0V
3.3
85
3.1
80
VIN=1.8V
VIN=1.5V
Efficiency (%)
Output Voltage (V)
3.2
3.0
2.9
VIN=1.2V
2.8
2.7
2.6
VIN=2.0V
75
70
VIN=1.8V
65
60
VIN=1.2V
2.5
VIN=0.9V
2.4
2.3
55
50
0
25
50
75
100
125
150
175
200
Output Current (mA)
VIN=1.5V
VIN=0.9V
0
25
50
75
100
125
150
175
200
Output Current (mA)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
7
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
AIC1638-33 Efficiency (L=47µH,CD54)
90
3.3
85
3.2
80
3.1
VIN=2.0V
VIN=1.8V
VIN=1.5V
Efficiency (%)
Output Voltage (V)
AIC1638-33 Load Regulation (L=47µH, CD54)
3.4
3.0
2.9
2.8
2.7
70
65
60
55
VIN=1.2V
VIN=0.9V
2.5
25
50
VIN=1.2V
45
40
0
75
100
125
150
175
200
225
0
25
50
75
150
175
200
225
250
3.50
1.1
3.45
1.0
Output Voltage Vout (V)
Start up
0.9
Input Voltage (V)
125
AIC1638-33 Output Voltage vs Temperature
AIC1638-33 Start-up & Hold-on Voltage (L=100µH)
0.8
0.7
0.6
0.5
Hold on
0.4
0.3
0.2
No Load
3.40
3.35
3.30
3.25
3.20
3.15
3.10
3.05
0.1
0
2
4
6
8
10
12
14
16
18
20
3.00
-40
-20
0
20
40
60
80
100
Temperature (°C)
Output Current (mA)
AIC1638-33 Switching Frequency vs Temperature
AIC1638-33 Maximum Duty Cycle vs Temperature
150
82
140
80
Maximum Duty Cycle (%)
Switching Frequency (kHz)
100
Output Current (mA)
Output Current (mA)
0.0
VIN=1.8V
VIN=1.5V
VIN=0.9V
50
2.6
2.4
VIN=2.0V
75
130
120
110
100
90
80
70
78
76
74
72
70
68
60
50
-40
-20
0
20
40
60
80
100
Temperature (°C)
66
-40
-20
0
20
40
60
80
100
Temperature (°C)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
8
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
AIC1638-33 Supply Current vs Temperature
60
1.6
56
Supply Current IDD1 (µA)
SW Turn On Resistance (Ω)
AIC1638-33 SW On Resistance vs Temperature
1.8
1.4
1.2
1.0
0.8
0.6
0.4
52
48
44
40
36
32
28
0.2
0.0
-40
-20
0
20
40
60
80
24
-40
100
-20
0
20
Temperature (°C)
5.0
90
4.0
VIN=1.5V
3.0
70
100
VIN=3.0V
VIN=2.0V
60
VIN=0.9V
VIN=1.5V
50
VIN=1.2V
VIN=1.2V
40
2.5
VIN=0.9V
2.0
1.5
80
80
VIN=3.0V
VIN=2.0V
Efficiency (%)
Output Voltage (V)
5.5
100
3.5
60
AIC1638-50 Efficiency (L=100µH,CD54)
AIC1638-50 Load Regulation ( L=100µH,CD54)
4.5
40
Temperature (°C)
30
0
50
100
150
200
250
300
350
20
400
0
50
100
150
200
250
300
350
400
Output Current (mA)
Output Current (mA)
AIC1638-50 Efficiency (L=47µH,CD54)
AIC1638-50 Load Regulation (L=47µH,CD54)
90
5.5
85
5.0
Efficiency (%)
Output Voltage (V)
80
VIN=3.0V
4.5
VIN=2.0V
4.0
3.5
VIN=1.5V
3.0
VIN=1.2V
2.5
70
VIN=3.0V
65
60
VIN=2.0V
55
VIN=0.9V
2.0
1.5
75
VIN=0.9V
50
0
50
100
150
200
250
300
350
400
Output Current (mA)
45
0
50
VIN=1.5V
VIN=1.2V
100
150
200
250
300
350
400
Output Current (mA)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
9
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
AIC1638-50 Output Voltage vs Temperature
AIC1638-50 Start-up & Hold-on Voltage (L=100µH)
5.3
1.8
5.2
Output Voltage Vout (V)
1.6
Input Voltage (V)
1.4
1.2
1.0
Start up
0.8
0.6
Hold on
0.4
5.0
4.9
4.8
4.7
4.6
4.5
0.2
0.0
No Load
5.1
0
2
4
6
8
10
12
14
16
18
4.4
-40
20
-20
0
Output Current (mA)
100
80
Maximum Duty Cycle (%)
Switching Frequency (kHz)
80
82
140
130
120
110
100
90
80
78
76
74
72
70
68
66
70
-20
0
20
40
60
80
64
-40
100
-20
0
Temperature (°C)
20
40
60
80
100
Temperature (°C)
AIC1638-50 Supply Current vs Temperature
AIC1638-50 SW On Resistance vs Temperature
100
1.6
90
1.4
Supply Current IDD1 µA)
SW Turn On Resistance (Ω)
60
AIC1638-50 Maximum Duty Cycle vs Temperature
AIC1638-50 Switching Frequency vs Temperature
150
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-40
40
Temperature (°C)
60
-40
20
80
70
60
50
40
30
20
-20
0
20
40
60
80
100
Temperature (°C)
10
-40
-20
0
20
40
60
80
100
Temperature (°C)
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
10
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
"
TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
VOUT
20mv/div
VOUT
50mV/div
VIN
0.5V/div
Load Step
50mA/div
Load Transient Response
Line Transient Response
(L=100µH, Co=47µF, VIN=2V)
BLOCK DIAGRAM
SW
1.25V REF.
VOUT
1M
+
Enable
GND
OSC, 100KHz
PIN DESCRIPTIONS
PIN1 : GND
- Ground. Must be low impedance;
sorder directly to ground plane.
PIN2 : VOUT
- IC supply pin. Connect VOUT to
the regulator output.
APPLICATION INFORMATION
GENERAL DESCRIPTION
AIC1638 PFM (pulse frequency modulation) controller
ICs combine a switch mode regulator, N-channel
power MOSFET, precision voltage reference, and
voltage detector in a single monolithic device. They
offer both extreme low quiescent current, high
efficiency, and very low gate threshold voltage to
PIN3 : SW – Internal drain of N-MOSFET switch.
ensure start-up with low battery voltage ( 0.8V typ.).
Designed to maximize battery life in portable products,
and minimize switching losses by only switching as
needed service the load.
PFM controllers transfer a discrete amount of energy
per cycle and regulate the output voltage by
modulating switching frequency with the constant
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
11
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
turn-on time. Switching frequency depends on load,
input voltage, and inductor value, and it can range up
to 100KHz. The SW on-resistance is typically 1 to 1.5
Ω to minimize switch losses.
When the output voltage drops, the error comparator
enables 100KHz oscillator that turns on the MOSFET
around 7.5us and 2.5µs off time. Turning on the
MOSFET allows inductor current to ramp up, storing
energy in a magnetic field. When MOSFET turns off
that force inductor current through diode to the output
capacitor and load. As the stored energy is depleted,
the current ramp down until the diode turns off. At this
point, inductor may ring due to residual energy and
stray capacitance. The output capacitor stores charge
when current flowing through the diode is high, and
release it when current is low, thereby maintaining a
steady voltage across the load.
As the load increases, the output capacitor discharges
faster and the error comparator initiates cycles sooner,
increasing the switching frequency. The maximum
duty cycle ensure adequate time for energy transfer to
output during the second half each cycle. Depending
on circuit, PFM controller can operate in either
discontinuous mode or continuous conduction mode.
Continuous conduction mode means that the inductor
current does not ramp to zero during each cycle.
VIN
IIN
IPK
ISW
ID
VSW
Charge Co.
IOUT
TDIS
Discharge Co.
t
Discontinuous Conduction Mode
VEXT
IIN
ID
IOUT
IIN
SW
+
EXT
VEXT
IPK
VOUT
IV
Isw
Ico
ISW
ID
IOUT
VSW
t
Continuous Conduction Mode
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
12
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
At the boundary between continuous and
discontinuous mode, output current (IOB) is
determined by
VIN

 1 VIN
IOB = 
TON(1− x )

 VOUT + VD  2 L
where VD is the diode drop,
x = (RON+Rs)Ton/L.
RON= Switch turn on resistance, Rs= Inductor DC
resistance
TON = Switch ON time
In the discontinuous mode, the switching frequency
(fsw) is
fsw =
2(L)(VOUT + VD − VIN)(IOUT)
(1+ x VIN 2 × TON 2
In the continuous mode, the switching frequency is
fsw =
1
(VOUT + VD − VIN) [1+ x (
TON (VOUT + VD − VSW)
≅
VIN − VSW
)]
2 VOUT + VD − VSW
1  VOUT + VD − VIN 


TON  VOUT + VD − VSW 
where Vsw = switch drop and proportion to output
current.
INDUCTOR SELECTION
Ron + Rs
 Vin 

IPK = 
Ton) 
 1 − exp( −
L
 Ron + Rs 

x
 VIN 

≅
(TON)1 − 
2
 L 

VIN
(Simple losses equation),
≅
TON
L
where x=(RON+RS)TON/L
1
EL = L × Ipk2
2
Power required from the inductor per cycle must be
equal or greater than
1
PL/fSW = (VOUT + VD − VIN)(IOUT)(
)
fSW
in order for the converter to regulate the output.
When loading is over IOB, PFM controller operates
in continuous mode. Inductor peak current can be
derived from
 VOUT + VD − VSW x 
−  IOUT +
IPK = 
VIN − VSW
2

 x
 VIN − VSW 
TON1 − 

2L

 2

Valley current (Iv) is
 VOUT + VD − VSW x 
 VIN − VSW 
Iv = 
− IOUT − 
×
−
IN
SW
2L
2
V
V




 x
TON1− 
 2
To operate as an efficient energy transfer element,
the inductor must fulfill three requirements. First, the
inductance must be low enough for the inductor to
store adequate energy under the worst case
condition of minimum input voltage and switch ON
time. Second, the inductance must also be high
enough so maximum current rating of AIC1638 and
inductor are not exceed at the other worst case
condition of maximum input voltage and ON time.
Lastly, the inductor must have sufficiently low DC
resistance so excessive power is not lost as heat in
the windings. But unfortunately this is inversely
related to physical size.
Minimum and Maximum input voltage, output voltage
and output current must be established before and
inductor can be selected.
In discontinuous mode operation, at the end of the
switch ON time, peak current and energy in the
inductor build according to
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
13
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
Table 1 Indicates resistance and height for each coil.
Power Inductor Type
DS1608
Coilcraft SMT Type
(www.coilcraft.com)
Inductance
( µH )
Resistance
(Ω)
Rated Current
(A)
22
0.10
0.7
47
0.18
0.5
100
0.38
0.3
22
0.08
2.7
47
0.14
1.8
47
0.25
0.7
100
0.50
0.5
47
0.25
0.7
100
0.50
0.5
33
0.11
1.2
Height
(mm)
DO3316
Sumida SMT Type CD54
Hold
SMT Type PM54
Hold
SMT Type PM75
2.9
5.2
4.5
4.5
5.0
CAPACITOR SELECTION
DIODE SELECTION
A poor choice for a output capacitor can result in
Speed, forward drop, and leakage current are the
poor efficiency and high output ripple. Ordinary
three main consideration in selecting a rectifier
aluminum electrolytic, while inexpensive may have
diode. Best performance is obtained with Schottky
unacceptably poor ESR and ESL. There are low
rectifier diode such 1N5819. Motorola makes
ESR aluminum capacitors for switch mode DC-DC
MBR0530 in surface mount. For lower output power
converters which work much better than general
a 1N4148 can be used although efficiency and
propose unit. Tantalum capacitors provide still better
start-up voltage will suffer substantially.
performance
at
more
expensive.
OS-CON
capacitors have extremely low ESR in a small size.
If capacitance is reduced, output ripple will increase.
COMPONENT POWER DISSIPATION
Operating in discontinuous mode, power loss in the
Most of the input supply is supplied by the input
winding resistance of inductor can be approximate
bypass capacitor, the capacitor voltage rating
equal to
should be at least 1.25 times greater than a
maximum input voltage.
PDL =
2  TON 
 VOUT + VD 

(Rs )
(POUT )
3 L 
 VOUT 
where POUT=VOUT * IOUT ; Rs=Inductor DC R;
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
14
AIC1638
3-PIN ONE-CELL STEP-UP DC/DC CONVERTER
SPEC NO: DS-1638-00 03/01/00
VD = Diode drop.
The power dissipated in rectifier diode is
The power dissipated in a switch loss is
 VD 
PDD = 
(POUT)
 VOUT 
PDsw =
2  TON 
 VOUT + VD − VIN 

(RON)
(POUT )
3 L 
VOUT


PHYSICAL DIMENSION
! SOT-89 (unit: mm)
D
A
SYMBOL
MIN
MAX
C
A
1.40
1.60
B
0.36
0.48
C
0.35
0.44
D
4.40
4.60
D1
1.62
1.83
E
2.29
2.60
D1
H
E
L
B
e
e1
e
1.50 (TYP.)
e1
3.00 (TYP.)
H
3.94
4.25
L
0.89
1.20
SYMBOL
MIN
MAX
A
4.32
5.33
SOT-89 MARKING
Part No.
AIC1638-27
AIC1638-30
AIC1638-33
AIC1638-50
Marking
AN27
AN30
AN33
AN50
! TO-92 (unit: mm)
A
E
L
C
C
e1
D
0.38 (TYP.)
D
4.40
5.20
E
3.17
4.20
e1
L
1.27 (TYP.)
12.7
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500 FAX:(8863)577-2510
-
15