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AIC1620/AIC1621/AIC1622
High Efficiency Synchronous Step-Up DC/DC Converter
n FEATURES
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n DESCRIPTION
The AIC1620/AIC1621/AIC1622 are high efficiency step up DC-DC converter. The start-up voltage is as low as 0.8V and operate with an input voltage down to 0.7V. Consuming only 20A of quiescent current. These devices offer a built-in synchronous rectifier that reduces size and cost by eliminating the need for an external Schottky diode and improves overall efficiency by minimizing losses. The switching frequency depends on the load and the input voltage can range up to 500KHz. The peak current of the internal switch is fixed at 0.8A (AIC1620), at 0.45A (AIC1621), or is selectable (AIC1622) for design flexibility. Ripple does not exceed the product of the switch current limit and the filter capacitor equivalent series resistance (ESR). The AIC1622 also features a circuit that eliminates noise due to inductor ringing.
High Efficiency 93% (V IN=2.4V, VOUT =3.3V, IOUT =200mA). 20A Quiescent Supply Current. Power-Saving Shutdown Mode (0.1A typical). Internal Synchronous Rectifier ( no external diode ) Selectable Current Limit for Reduced Ripple ( AIC1622 ). Low Noise , Anti-Ringing Feature ( AIC1622 ) On-Chip Low Battery Detector. Low Battery Hysteresis
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n APPLICATIONS
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Palmtop & Notebook Computers. PDAs Wireless Phones Pocket Organizers. Cameras. 1 to 2-Cell Hand-Held Devices
n TYPICAL APPLICATION CIRCUIT
VIN + 100F OFF SHDN AIC1620 AIC1621 AIC1622 LX OUT 22H Output 3.3V, or Adj. (1.8V to 4.0V) up to 300mA
ON
+ 220F
Low-Battery Detect In
LBI REF 0.1F
LBO FB LBO GND FB
Low-Battery Detect Out
Analog Integrations Corporation
4F, 9 Industry E. 9th Rd, Science-Based Industrial Park, Hsinchu, Taiwan TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw
DS-1620-00 032502
1
AIC1620/AIC1621/AIC1622
n ORDERING INFORMATION
AIC1620CX XX AIC1621C X XX AIC1622C X XX PACKING TYPE TR: TAPE & REEL PACKAGING TYPE O: MSOP8 (for AIC1620/1) O: MSOP10 (for AIC1622)
PIN CONFIGURATION
(MSOP8)
FB 1 LBI 2 LBO 3 REF 4 TOP VIEW 8 OUT LX GND SHDN
AIC1620 AIC1621
7 6 5
(MSOP10)
FB 1
TOP VIEW
10 OUT
Example: AIC1620COTR a In MSO8 Package & Taping & Reel Packing Type
LBI 2 LBO 3 CLSEL 4 REF 5
9 LX
AIC1622
8 7 6
GND BATT SHDN
n ABSOLUTE MAXIMUM RATINGS
Supply Voltage (OUT to GND) Switch Voltage (LX to GND) Battery Voltage (Batt to GND) SHDN , LBO to GND LBI, REF, FB, CLSEL to GND Switch Current (LX) Output Current (OUT) Operating Temperature Range Storage Temperature Range 8.0V VOUT + 0.3V 6.0V 6.0V VOUT +0.3V -1.5A to +1.5A -1.5A to +1.5A -40C ~ +85C -65C ~150C
n TEST CIRCUIT
Refer to Typical Application Circuit.
2
AIC1620/AIC1621/AIC1622
n ELECTRICAL CHARACTERISTICS (V
TA=25C, unless otherwise specified.)
BATT=2.0V,
VOUT=3.3V (FB=VOUT), RL=,
PARAMETER
Minimum Input Voltage Operating Voltage Start-Up Voltage Start-Up Voltage Tempco Output Voltage Range Output Voltage Steady State Output Current (Note 2) Reference Voltage Reference Voltage Tempco Reference Load Regulation Reference Line Regulation FB , LBI Input Threshold Internal switch On-Resistance LX Switch Current Limit
TEST CONDITIONS
MIN.
TYP.
0.7
MAX.
UNIT
V
1.1 RL=3K (Note1) 0.8 -2 1.8 FB = VOUT FB=OUT AIC1620 AIC1622 (CLSEL=OUT) AIC1622 (CLSEL=GND) IREF= 0 3.17 300 150 1.199 3.3 400
4.0 1.1
V V mV/C
4.0 3.43 V
(VOUT =3.3V) AIC1621
mA 220 1.23 0.024 1.261 V mV/C 30 10 1.261 mV mV/V V 1.0 A 0.6 1 35 A A
IREF = 0 to 100 A VOUT = 1.8V to 4V 1.199 ILX = 100mA AIC1620,AIC1622(CLSEL = OUT) AIC1621,AIC1622(CLSEL = GND) 0.6 0.3
10 5 1.23 0.3 0.8 0.45 0.05 20
LX Leakage Current Operating Current into OUT (Note 3) Shutdown Current into OUT Efficiency
VLX=0V, 4V; VOUT =4V VFB = 1.4V , VOUT = 3.3V
SHDN = GND VOUT = 3.3V ,ILOAD = 200mA VOUT = 2V ,ILOAD = 1mA
0.1 90
1
A %
85 2 0.6 4 0.9 0.03 7 1.3 50 S S nA
LX Switch On-Time LX Switch Off-Time FB Input Current
VFB =1V , VOUT = 3.3V VFB =1V , VOUT = 3.3V VFB = 1.4V
3
AIC1620/AIC1621/AIC1622
n ELECTRICAL CHARACTERISTICS (Continued)
PARAMETER
LBI Input Current CLSEL Input Current
TEST CONDITIONS
VLBI = 1.4V AIC1622 , CLSEL = OUT V SHDN = 0 or VOUT VLBI = 0, ISINK = 1mA V LBO = 5.5V, VLBI = 5.5V
MIN.
TYP.
1 1.4 0.07 0.2 0.07 50
MAX.
50 3 50 0.4 1
UNIT
nA A nA A
SHDN Input Current LBO Low Output Voltage LBO Off Leakage Current
LBI Hystereisis Damping Switch Resistance
mV 100 0.2VOUT V
AIC1622, VBATT = 2V
50
SHDN Input Voltage
0.8V OUT 0.2VOUT CLSEL Input Voltage 0.8V OUT
V
Note 1: Start-up voltage operation is guaranteed without the addition of an external Schottky diode between the input and output. Note 2: Steady-state output current indicates that the device maintains output voltage regulation under load. Note 3: Device is bootstrapped (power to the IC comes from OUT). This correlates directly with the actual battery supply.
n TYPICAL PERFORMANCE CHARACTERISTICS
100 90 80 160 140 120 100 80 60 40 20 0 0.0
Efficiency (%)
70 60 50 40 30 20 10 0 0.01 0.1 1
V IN=2.4V VIN=1.2V
Input Battery Current (A)
I_limit=0.8A , VOUT=3.3V
I_limit=0.45A , V OUT=3.3V
0.5 1.0 1.5 2.0 2.5 3.0
10
100
1000
Loading (mA)
Input battery voltage (V)
Fig. 1
VOUT =3.3V
CLSEL=OUT (0.8A)
Fig. 2
No-Load Battery Current vs. Input Battery Voltage
4
AIC1620/AIC1621/AIC1622
n TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
100
1.8 1.6
90
80
Start-up Voltage (V)
1.4 1.2 1.0 0.8 0.6 0.4
Efficiency (%)
V IN =2.4V
70
Without Diode
V IN =1.2V
60
With Diode
50
0.2
40 0.01
0.1
1
10
100
1000
0.0 0.01
0.1
1
10
100
Loading (mA) Fig. 3 VOUT=3.3V CLSEL=GND (0.45A)
0.10 0.08 2.2 2.0
Load Current (mA)
Fig. 4 Start-up Voltage vs. Load Current
Shutdown Current (A)
0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Shutdown Threshold (V)
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Fig. 5
800
VOUT (V) Shutdown Current vs. VOUT
Output Voltage (V)
Fig. 6
Shutdown Threshold vs. Output Voltage
Maximum Output Current (mA)
700 600
VOUT=3.3V
CLSEL=OUT
LX pin waveform
500 400 300 200 100 0 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VOUT AC Couple
CLSEL=GND
Inductor Current
VIN =2.4V VOUT =3.3V
Input Voltage (V)
Fig. 7
Maximum Output Current vs. Input Voltage
Fig. 8 Heavy Load Waveform
5
AIC1620/AIC1621/AIC1622
n TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
Fig. 9
Without Damping Ringing Function
Fig. 10 With Damping Ringing Function
VIN =2.4V VOUT=3.3V
IOUT=200mA
VOUT AC Couple
Fig. 11 Load Transient Response
6
AIC1620/AIC1621/AIC1622
n BLOCK DIAGRAM
SHDN CLSEL Minimum Off-Time One Shot + Q1 Damping Switch Q3 OUT 0.1F R1 BATT 200 LX L 1 47F OUT C3 220F
VIN + C1 100F
F/F S R One Shot Maximum On-Time + Q
Q2
GND
Mirror
FB + + LBO Reference Voltage REF C4 0.1F
LBI
n PIN DESCRIPTIONS
AIC1620/ AIC1621 PIN 1: FBConnect to OUT for +3.3V output. Use a resistor network to set the output voltage from +1.8V to +4.0V. PIN 2: LBILow-battery comparator input. nterI nally set to trip at +1.23V. PIN 3: LBO- Open-drain low battery comparator output. Output is low when V is LBI <1.23V. LBO is high impedance during shutdown. PIN 4: REF1.23V reference voltage. Bypass with a 0.1F capacitor. PIN 5: SHDN- Shutdown input. High=operating, low=shutdown. PIN 6: GND- Ground PIN 7: LXN-channel and P-channel power MOSFET drain. PIN 8: OUT- Power output. OUT provides bootstrap power to the IC.
7
AIC1620/AIC1621/AIC1622
AIC1622 PIN 1: FB-
Connect to OUT for +3.3V output. Use a resistor network to set the output voltage from +1.8V to +4.0V. PIN 2: LBILow-Battery comparator input. I tern nally set to trip at +1.23V. PIN 3: LBO- Open-drain low battery comparator output. Output is low when VLBI is <1.23V. LBO is high impedance during shutdown. PIN 4: CLSEL- Current-limit selects input. CLSEL= OUT sets the current limit to 0.8A. CLSEL=GND sets the current limit to 0.45A.
PIN 5: REF-
1.23V reference voltage. Bypass with a 0.1F capacitor. PIN 6: SHDN- Shutdown input. High=operating, low=shutdown. PIN 7: BATT- Battery input and damping switch connection. If damping switch is unused, leave BATT unconnected. PIN 8: GND- Ground. PIN 9: LXN-channel and P-channel power MOSFET drain. PIN 10: OUT- Power output. OUT provides bootstrap power to the IC.
n APPLICATION INFORMATION
Overview
The AIC1620/AIC1621/AIC1622 series are high efficiency, step-up DC-DC converters, designed to feature a built-in synchronous rectifier, which reduces size and cost by eliminating the need for an external Schottky diode. The start-up voltage is as low as 0.9V and operate with an input voltage down to 0.7V. Quiescent supply current is only 20A. In addition, the AIC1622 feature a circuit that eliminates inductor ring to reduce noise. The internal P-MOSFET onresistance is typically 0.3 to improve overall efficiency by minimizing AC losses. The current limit of the AIC1620 and AIC1621 are 0.8A and 0.45A respectively. The AIC1622 offers a selectable current limit(0.45A or 0.8A). The lower current limit allows the use of a physically smaller inductor in spacesensitive applications.
PFM Control Scheme
The key feature of the AIC1620 series is a unique minimum-off-time, current-limited, pulse-frequencymodulation (PFM) control scheme (see BLOCK DIAGRAM) with the ultra-low quiescent current . A constant-peak-current limit in the switching allows the inductor current to vary between this peak limit and some lesser value. The peak current of the internal NMOSFET power switch can be fixed at 0.8A, 0.45A or is selectable. Besides, the ripple voltage dose not exceed the product of the peak current limit and the filter capacitor equivalent series resistance (ESR). The switch frequency depends on the loading condition and input voltage, and can range up to 500KHz. The switching frequency is governed by a pair of oneshots that set a minimum off-time (1S) and a maximum on-time (4S).
8
AIC1620/AIC1621/AIC1622
Synchronous Rectification
Using the internal synchronous rectifier eliminates the need for an external Schottky diode. Therefore, the cost and board space is reduced. During the cycle of off-time, the P-MOSFET turns on and shunts the NMOSFET. Due to the low turn-on resistance of MOSFET, the synchronous rectifier significantly improves efficiency without the addition of an external component. Thus, the conversion efficiency can be as high as 93%.
BATT/Damping Switch
The AIC1622 is designed with an internal damping switch (Fig. 15) to reduce ringing at LX. The damping switch supply a path to quickly dissipate the energy stored in inductor and reduces the ringing at LX. Damping LX ringing dose not reduce VOUT ripple, but dose reduce EMI. R1=200 works well for most a pplication while reducing efficiency by only 1%. Larger R1 value provide less damping, but less impact on efficiency. In principle, lower value of R1 is needed to fully damp LX when the VOUT /VIN ratio is high.
Reference Voltage
The reference voltage (REF) is nominally 1.23V for excellent T.C. performance. In addition, REF pin can source up to 100A to external circuit with good load regulation (<10mV). A bypass capacitor of 0.1F is required for proper operation and good performance
Selecting the Output Voltage
VOUT can be simply set to 3.3V by connecting the FB pin to OUT due to internal resistor divider (Fig. 16). In order to adjust the output voltage, a resistor divider is connected to VOUT, FB, GND (Fig. 17). Use the following equation to calculate:
Shutdown
The whole circuit is shutdown when VSHDN is low. During shutdown mode, the current can flow from the battery to the output due to body diode of the PMOSFET. VOUT falls to approximately Vin-0.6V and LX remains high impedance. The capacitance and load at OUT determine the rate at which VOUT decays. Shutdown can be pulled as high as 6V. Regardless of the voltage at OUT.
R5=R6 [(V OUT / VREF )-1] Where VREF =1.23V and VOUT may range from 1.8V to 4V.
Low-Battery Detection
The AIC1620 series contain an on-chip comparator with 50mV internal hysteresis (REF, REF+50mV) for low battery detection. If the voltage at LBI falls below the internal reference voltage. LBO ( an open-drain output) sinks current to GND.
Current Limit Select Pin
The AIC1622 series allows a selectable inductor current limit of either 0.45A or 0.8A. This allows flexibility in designing for higher current or smaller applications. CLSEL draws 1.4A when connected to OUT.
9
AIC1620/AIC1621/AIC1622
Component Selection
1. Inductor Selection An inductor value of 22H performs well in most applications. The AIC1620 series also work with inductors in the 10H to 47H range. An inductor with higher peak inductor current tends a higher output voltage ripple (IPEAKN output filter capacitor ESR). The inductor' DC resistance significantly s affects efficiency. We can calculate the maximum output current as follows: VIN VOUT - VIN IOUT ( MAX) = ILIM - t OFF VOUT 2 xL amps VIN=input voltage L=inductor value in H b=efficiency (typically 0.9) tOFF=LX switch'off-time in S ILIM =0.45A or 0.8A be. A filter capacitor with low ESR is helpful to the efficiency and steady state output current of AIC1620 series. Therefore HERMEI capacitor LT series with 220F/6.3V is recommended. A smaller capacitor (down to 10F with higher ESR) is acceptable for light loads or in applications that can tolerate higher output ripple. 3. PCB Layout and Grounding Since AIC1622' switching frequency can range s up to 500kHz, it makes AIC1622 become very sensitive. So careful printed circuit layout is mi portant for minimizing ground bounce and noise. IC' OUT pin should be as clear as possible. And s the GND pin should be placed close to the ground plane. Keep the IC' GND pin and the ground s leads of the input and output filter capacitors less than 0.2in (5mm) apart. In addition, keep all connection to the FB and LX pins as short as possible. In particular, when using external feedback resistors, locate them as close to the FB as pos2. Capacitor Selection The output voltage ripple relates with the peak inductor current and the output capacitor ESR. Besides output ripple voltage, the output ripple current also needs to be concerned. The smaller the capacitor ESR is, the higher the ripple current will sible. To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the IC' GND directly to the s ground plane. Following are the recommended layout diagrams.

where IOUT(MAX)=maximum output current in
Figure 12. Top layer
Figure 13. Bottom layer
Figure 14. Placement
10
AIC1620/AIC1621/AIC1622
n APPLICATION EXAMPLES
VOUT
VIN R1 200
R1 200 VIN LX
L1 22 H
L 22H BATT (AIC1622) LX OUT CLSEL (AIC1622) SHDN C2 0.1F R2 100K LBO GND AIC1620 AIC1621 AIC1622 FB
Q1
OUT DAMPING SWITCH Q3 BATT
C1 100F VOUT C3 220F
R3 LBI R4 REF 0.1 F C4
Q2 AIC1622 GND
LOW BATTERY OUTPUT
Fig. 15. Simplified Damping Switch Diagram
Fig. 16 VOUT = 3.3V Application Circuit.
VIN R1 200 L 22H BATT (AIC1622) LX OUT CLSEL (AIC1622) SHDN R4 0.1F C4 REF LBO GND AIC1620 AIC1621 AIC1622 FB LOW BATTERY OUTPUT R6 100K R2 C2 0.1 F R5 VOUT C3 220F C1 100F
R3 LBI
Fig. 17 An Adjustable Output Application Circuit
11
AIC1620/AIC1621/AIC1622
n PHYSICAL DIMENSION
l 8 LEAD MSOP (unit: mm)
D
SYMBOL A1 A2
E E1
MIN -0.76 0.28 0.13 2.90 4.80 2.90 0.65 0.40
MAX 0.20 0.97 0.38 0.23 3.10 5.00 3.10 0.66
b C D E E1
e A2 C A1
e L
L
b
l
10 LEAD MSOP (unit: mm)
D
SYMBOL A1 A2
E E1
MIN -0.76 0.15 0.13 2.90 4.80 2.90 0.50 0.40
MAX 0.20 0.97 0.30 0.23 3.10 5.00 3.10 0.66
b C D E E1
e A2 C A1
e L
L
b
12

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