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AIC1896
1. 4MHz Thin Package Current-Mode Step-Up DC/DC Converter
FEATURES
Fixed Frequency 1.4MHz Current-Mode PWM Operation. Adjustable Output Voltage up to 30V. Guaranteed 13V/ 200mA Output with 5V Input. 2.5V to 10V Input Range. Maximum 0.1A Shutdown Current. Programmable Soft-Start. Tiny Inductor and Capacitors are allowed. Space-Saving SOT-23-6 and TSOT-23-6 Package. The high switching frequency (1.4MHz) allows the use of small external components. The Soft-Start function is programmable with an external capacitor, which sets the input current ramp rate. The AIC1896 is available in a space-saving SOT-23-6 and TSOT-23-6 package.
DESCRIPTION
AIC1896 is a current-mode pulse-width modulation (PWM), step-up DC/DC Converter. The built-in high voltage N-channel MOSFET allows AIC1896 for step-up applications with up to 30V output voltage, as well as for Single Ended Primary Inductance Converter (SEPIC) and other low-side switching DC/DC converter.
APPLICATIONS
White LED Backlight. OLED Driver. LCD Bias
TYPICAL APPLICATION CIRCUIT
VIN 3.3V or 4.2V C1 4.7F AIC1896
6
L
D1
CH521S-30
86
C3 1F
ZD1
BZV55-B12 11.8V~12.2V
84 82
Efficiency (%)
80 78 76 74 72 70 68 2 4 6 8
IN
LX
1 3
VIN=4.2V VIN=3.3V
OFF ON
4
SHDN FB SS GND
5 2
R2 1K 62 ILED R1
C2 0.033F
L: GTSK-51-150M (15H) L: GTSK-51-100M (10H)
10 12 14 16 18 20
LED Current (mA)
Fig. 1 Li-Ion Powered Driver for three white LEDs
Analog Integrations Corporation
Si-Soft Research Center 3A1, No.1, Li-Hsin Rd. I, Science Park, Hsinchu 300, Taiwan, R.O.C. TEL: 886-3-5772500 FAX: 886-3-5772510 www.analog.com.tw
DS-1896G-01
121208
1
AIC1896
VIN 3.6V or 4.2V C1 4.7F
L
D1
CH521S-30
80
C3 1F
78 76
ZD1
BZV55-B24 23.5V~24.5V
AIC1896
6 OFF ON 4
Efficiency (%)
74 72 70 68 66 64 62 60 2 4 6 8
IN
LX
1 3
VIN=4.2V VIN=3.6V
SHDN FB SS GND
5 2
R2 1K R1 62 ILED
C2 0.033F
L: GTSK-51-150M (15H) L: GTSK-51-100M (10H)
10 12 14 16 18 20
LED Current (mA)
Fig. 2 Li-Ion Powered Driver for six white LEDs
ORDERING INFORMATION
AIC1896XXXX PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE G: SOT-23-6 K: TSOT-23-6 P: LEAD FREE COMMERCIAL G: GREEN PACKAGE Example: AIC1896PKTR in Lead Free TSOT-23-6 Package & Tape & Reel Packing Type AIC1896PGTR in Lead Free SOT-23-6 Package & Tape & Reel Packing Type PIN CONFIGURATION SOT-23-6 / TSOT-23-6 FRONT VIEW 6 5 4 1: LX 2: GND 3: FB 1896/1896P 4: SHDN 5: SS 2 1 3 6: IN
Note: Pin1 is determined by orienting the package marking as shown.
TSOT-23-6 Marking
Part No. AIC1896PK AIC1896GK Marking 896PK 896GK
SOT-23-6 Marking
Part No. AIC1896PG AIC1896GG Marking 1896P 1896G
2
AIC1896
ABSOLUTE MAXIMUM RATINGS
LX to GND FB to GND IN, SHDN SS to GND LX Pin RMS Current Continuous Power Dissipation Operating Temperature Range Junction Temperature Storage Temperature Range Lead Temperature (soldering, 10s) -0.3V to +33V -0.3V to +6V -0.3V to +11V -0.3V to +6V 0.6A 727mW -40 to 85 C C 125C -65 to 150 C C 260C
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
TEST CIRCUIT
L1 VIN 2.5V to 10V + C1 10F/16V
D1 VOUT SS14 C3
1 3
GTSK-51-100M(10uH)
+ R1 C4 10F C5 1F
U1 AIC1896
6 4
IN SHDN SS
5
LX FB GND
2
SHDN C2 0.033F
R2 62
3
AIC1896
ELECTRICAL CHARACTERISTICS
(VIN=V SHDN =3V, FB=GND, SS=Open, TA=25C, unless otherwise specified) (Note 1)
PARAMETER Input Supply Range Output Voltage Adjust Range VIN Undervoltage Lockout Quiescent Current Shutdown Supply Current ERROR AMPLIFIER Feedback Regulation Set Point FB Input Bias Current Line Regulation OSCILLATOR Frequency Maximum Duty Cycle POWER SWITCH Steady State Output Current On-Resistance Leakage Current SOFT-START Reset Switch Resistance Charge Current CONTROL INPUT Input Low Voltage Input High Voltage VIL VIH I SHDN V SHDN , VIN = 2.5V to 10V V SHDN , VIN = 2.5V to 10V V SHDN = 1.8V V SHDN = 0 1.0 25 0.01 50 0.1 0.3 V V A Guaranteed By Design VSS = 1.2V 1.5 4 100 7.0 A Io Refer to Fig. 13 1 0.1 1.4 1 10 VLX = 30V, TA = +25C VLX = 30V A A RDS(ON) Vin = 5V ILX(OFF) fOSC DC 1000 82 1400 86 1800 KHz % VFB IFB VFB = 1.24V 2.6V < VIN < 5.5V 1.205 1.23 21 0.05 1.255 80 0.20 V nA %/V
SYMBOL
CONDITIONS
MIN 2.5
TYP
MAX UNITS 10 30 V V V 0.2 5 0.5 10 mA A A
VIN VOUT UVLO VIN rising, 50mV hysteresis IIN VFB = 1.3V, not switching VFB = 1.0V, switching V SHDN = 0, TA = +25C V SHDN = 0
2.2 0.1 1 0.01 0.01
SHDN Input Current
Note 1: Specifications are production tested at TA=25C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC).
4
AIC1896
TYPICAL PERFORMANCE CHARACTERISTICS
1.50
1.50
Switching Frequency (MHz)
1.45
TA=25C Frequency (MHz)
VIN=3.6V
1.45
1.40
1.35
1.40
1.30
1.35
1.25
1.20 -40 -20 0 20 40 60 80 100
1.30
2
3
4
5
6
7
8
9
10
11
Temperature (C) Fig. 3 Switching Frequency vs. Temperature
1.7 1.6 5.50
Supply Voltage (V) Fig. 4 Frequency vs. Supply Voltage
VIN=3.6V Output Voltage (V)
2 3 4 5 6 7 8 9 10 11 5.25
1.5
RDS(ON) ()
1.4 1.3 1.2 1.1 1.0 0.9 0.8
5.00
4.75
4.50 1 10 100
Supply Voltage (V) Fig. 5 RDSON vs. Supply Voltage
12.5
2.4
Output Current (mA) Fig. 6 Load Regulation (L1=10H)
VIN=3.6V Output Voltage (V)
Supply Current (mA)
12.0
2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6
FB=1.0V SHDN=1.0V
11.5
11.0
10.5
1
10
100
2
3
4
5
6
7
8
9
10
11
Output Current (mA) Fig. 7 Load Regulation (L1=22H)
Supply Voltage (V) Fig. 8 Switching Current
5
AIC1896
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
1.25
90
85
80
FB=1.3V SHDN=1.0V
Feedback Voltage (V)
Supply Current (
A)
1.24
1.23
75
1.22
70
1.21
VIN=3.6V
65 2 3 4 5 6 7 8 9 10 11
1.20 -50
-25
0
25
50
75
100
Supply Voltage (V) Fig. 9 Non-Switching Current
Temperature (C) Fig. 10 Feedback Pin Voltage
90 85
90
Efficiency (%)
Efficiency (%)
80 75 70 65 60 0
VIN=2.7V VIN=2.5V
VIN=4.2V VIN=3.6V VIN=3.3V
85 80 75 70 65 60
VIN=4.2V VIN=3.6V VIN=3.3V
VIN=5.0V
VOUT=5.0V L1: GTSK-51-100M
100 200 300 400 500 600
VOUT=12V L1: SLF6025-220MR
0 50 100 150 200
Output Current (mA) Fig. 11 Efficiency vs. Output Current (L1=10H, test circuit refer to p.3)
800
Output Current (mA) Fig. 12 Efficiency vs. output current (L1=22H, test circuit refer to p.3)
350
Maximum Output Current (mA)
700
Maximum Output Current (mA)
300 250
VOUT=5V
600
VOUT=13V VOUT=9V
VOUT=20V VOUT=25V
500 400 300 200 100
VOUT=15V
200 150 100 50 0 3 4 5 6
VOUT=30V Maximum output current defined at 90% of no load output voltage
7 8 9 10 11
Maximum output current defined at 90% of no load output voltage
2 3 4 5 6 7 8 9 10
Supply Voltage (V)
Supply Voltage (V) Fig. 13(b) Maximum Output Current vs. Supply Voltage (L1:22H, test circuit refer to p.3)
Fig. 13(a) Maximum Output current vs. Supply Voltage (L1: 10H, test circuit refer to p.3)
6
AIC1896
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
VLX
VSW
VOUT
VOUT ILX
ILX
Fig. 14 Operation Wave Form (VIN=5V; VOUT=12V, L1=22H; R1=105K; R2=12K;C3=1nF;IOUT=200mA, test circuit refer to p.3)
Fig. 15 Operation Wave Form (VIN=3V;VOUT=5V;L1=10H;R1=36K;R2=12K; C3=39pF;IOUT=200mA, test circuit refer to p.3)
VOUT
VOUT
ILX
ILX
Fig. 16 Load Step Response (VIN=3.3V; VOUT=5V;L1=10H;IOUT=5mA to 200mA, test circuit refer to p.3)
Fig. 17 Load Step Response (VIN=5V ; VOUT=12V ;L1=22H;IOUT=5mA to 150mA, test circuit refer to p.3)
SHDN
VOUT
ILX
Fig. 18 Start-Up from Shutdown (VIN=3.3V ;VOUT=13V ;RLOAD=300, test circuit refer to p.3)
7
AIC1896
BLOCK DIAGRAM
VIN Control
PWM/PFM
I9
Soft Start
R3 R4
Error Amp + Q1
SS
4A
PWM Comparator
+ Control Logic Driver
SHDN
FB
1
Q2
8
RC
CC 1.4MHz
R1
LX x1 RS GND x20
Oscillator
R2 Slope Compensation Current AMP x 5 + -
PIN DESCRIPTIONS
PIN 1: LX Power Switching Connection. Connect LX to inductor and output rectifier. Keep the distance between the components as close to LX as possible. Ground. Feedback Input. Connect a resistive voltage-divider from the output to FB to set the output voltage.
SHDN with a slew rate of 0.1V/s or greater. Do not leave SHDN unconnected. SHDN draws up to 50A.
PIN 5: SS Soft-Start Input. Connect a soft-start capacitor from SS to GND in order to soft-start the converter. Leave SS open to disable the soft-start function. Internal Bias Voltage Input. Connect IN to the input voltage source. Bypass IN to GND with a capacitor sitting as close to IN as possible.
PIN 2: GND PIN 3: FB -
PIN 6: IN
-
PIN 4: SHDN - Shutdown Input. Drive SHDN low to turn off the converter. To automatically start the converter, connect SHDN to IN. Drive
8
AIC1896
APPLICATION INFORMATION
Inductor Selection
A 15H inductor is recommended for most AIC1896 applications. Although small size and high efficiency are major concerns, the inductor should have low core losses at 1.4MHz and low DCR (copper wire resistance). accurate LED current, precision resistors are preferred (1% recommended). The formula for R1 selection is shown below. R1 = 1.23V/ILED (1)
Open-Circuit Protection
In the cases of output open circuit, when the LEDs are disconnected from the circuit or the LEDs fail, the feedback voltage will be zero. AIC1896 will then switch to a high duty cycle resulting in a high output voltage, which may cause SW pin voltage to exceed its maximum 30V rating. A zener diode can be used at the output to limit the voltage on SW pin (Fig. 20). The zener voltage should be larger than the maximum forward voltage of the LED string. The current rating of the zener should be larger than 0.1mA.
Capacitor Selection
The small size of ceramic capacitors makes them ideal for AIC1896 applications. X5R and X7R types are recommended because they retain their capacitance over wider ranges of voltage and temperature than other types, such as Y5V or Z5U. A 4.7F input capacitor and a 1F output capacitor are sufficient for most AIC1896 applications.
Diode Selection
Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AIC1896 applications. The forward voltage drop of a Schottky diode represents the conduction losses in the diode, while the diode capacitance (CT or CD) represents the switching losses. For diode selection, both forward voltage drop and diode capacitance need to be considered. Schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause significant switching losses at the 1.4MHz switching frequency of AIC1896. A Schottky diode rated at 100mA to 200mA is sufficient for most AIC1896 applications.
Dimming Control
There are three different types of dimming control circuits as follows:
1. Using a PWM signal
PWM brightness control provides the widest dimming range by pulsing LEDs on and off at full and zero current, repectively. The change of average LED current depends on the duty cycle of the PWM signal. Typically, a 0.1kHz to 10kHz PWM signal is used. Two applications of PWM dimming with AIC 1896 are shown in Fig 21. One, as fig. 21(a), uses PWM signal to drive SHDN pin directly for dimming control. The other, as fig. 21(b), employs PWM signal going through a resistor to drive FB pin. If the SHDN pin is used, the increase of duty cycle results in LED brightness enhancement. If the FB pin is used, on the contrary, the increase of duty cycle will decrease its brightness. In this application, LEDs
LED Current Control
LED current is controlled by feedback resistor (R1 in Fig. 1). The feedback reference is 1.23V. The LED current is 1.23V/R1. In order to have
9
AIC1896
are dimmed by FB pin and turned off completely by
the FB pin bias current. With a VDC ranging from 0V to 5V, the selection of resistors in Fig. 22 results in dimming control of LED current from 20mA to 0mA, respectively.
SHDN .
2. Using a DC Voltage
For some applications, the preferred method of a dimming control uses a variable DC voltage to adjust LED current. A dimming control using a DC voltage is shown as Fig. 22. As DC voltage increases, the voltage drop over R2 increases and the voltage drop over R1 decreases. Cautiously selecting R2 and R3 is essential so that the current from the variable DC source is much smaller than the LED current and much larger than
L1 VIN 3.3V to 4.2V C1 4.7F U1
6 4
3. Using a Filtered PWM Signal
Filtered PWM signal can be considered as an adjustable DC voltage. It can be used to replace the variable DC voltage source in dimming control. The circuit is shown in Fig. 23.
10H
D1
SS0540
SLF6025-100M1R0
C3 ZD1
BZV55-B24
1F
AIC1896 LX FB GND
5 2
23.5V~24.5V
1 3
IN SHDN SS
OFF
ON
R2 1K
IOUT=ILED=20mA R1 62
C2 0.033F
Fig. 19 White LED Driver with Open-Circuit Protection
AIC1896 IN PWM SHDN SS LX
ZD1
AIC1896 IN LX
ZD1
R2 FB 1K GND R1 62 C2
C2 0.033F OFF ON SHDN SS FB
R2 1K GND R3 30K R1 62
0.033F
PWM
(a) Fig. 20 Dimming Control Using a PWM Signal
(b)
10
AIC1896
AIC1896
AIC1896 IN SHDN OFF ON SS GND R3 C2 0.033F LX R2 FB 1K R1 82 20mA~0mA ZD1
ZD1
IN SHDN OFF ON SS
LX R2 FB 1K GND R3 3.3K R4 4K C1 0.1F R1 82
C2 0.033F
3.3K
VDC 0V~5V
PWM
Fig. 21 Dimming Control Using a DC Voltage
Fig. 22 Dimming Control Using a Filtered PWM Signal
APPLICATION EXAMPLES
VIN 3V to 4.2V C1 4.7F
L1
10H
D1
SS0504
SLF6025-100M1R0
C3 ZD1 U1 AIC1896
6 4
1F
BZV55-B24 23.5V~24.5V
1 3
IN SHDN SS
5
LX FB GND
2
OFF ON
R2 1K IOUT=ILED=20mA
C2 0.033F
R1 62
R3 62
Fig. 23
1-Cell Li-Ion Powered Driver for eight White LEDs with Open-Circuit Protection
11
AIC1896
* L1 AIC1896 Vin C1 33uF + IN LX
D1
SS14 + * R2 C4 10u/25V
Vout Vout C5 0.1uF 5V 9V 12V 18V 24V *R2 36K 75k 105k 160k 220k *L1 10uH 10uH 10uH 22uH 22uH
/SHDN FB SS GND R1 12k
C3 100p
C2 0.033uF
Fig. 24 Typical Step up Application Circuit
VOUT2 D2 BAT54S L1 VIN 3V to 4.2V C4 4.7F/6.3V 6 4 OFF ON 22uH C1 1F -15V/5mA C2 1F/16V
SLF6025-220MR73 AIC1896 IN LX
1 3
D1 R2 135k R1 12k C6
SS0540
VOUT1 +15V/5mA C3 1F/16V
SHDN FB SS GND 5 2
100pF
C5 0.033F
L1 5VIN C1 4.7uF U1 22uH IN SHDN GND AIC1896 SW FB R2 SS C2 10nF 91k D1 SS054 C5 0.01u R1 3M
Fig. 26 High 40V Output Voltage for Electrophoretic Display (EPD) Application
Fig. 25 1-Cell Li-Ion to
15V/5mA Dual Output Converter for LCD Bias
VOUT=40V/10mA C4 0.1uF
D2 BAT54S C3 0.01u
12
AIC1896
D3 C6 1uF BAT54WS C7 1uF R3 2.2K
Q2 MMBT2907A C11 1uF D5 7.7V
Vout3=-7V
D2 C8 1uF L1 Vin C1 4.7uF SW 22uH AIC1896 IN LX R1 85K C3 100pF C2 0.033uF C4 10uF/25V + C5 0.1uF Vout1=10V D1 SS14 BAT54WS C9 1uF Vout2=20V
/SHDN FB SS GND R2 12K
Fig. 27 Three output voltage for LCD
13
PHYSICAL DIMENSIONS (unit: mm)
TSOT-23-6
AIC1896
14
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AIC1896
SOT-23-6
D
Note:
Information provided by AIC is believed to be accurate and reliable. However, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AIC product; nor for any infringement of patents or other rights of third parties that may result from its use. We reserve the right to change the circuitry and specifications without notice. Life Support Policy: AIC does not authorize any AIC product for use in life support devices and/or systems. Life support devices or systems are devices or systems which, (I) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
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