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FEATURES
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AIC1848
Regulated 5V Charge Pump In SOT-23
DESCRIPTION
The AIC1848 charge pump is a micropower charge pump DC/DC converter that produces a regulated output voltage from 2.7V to 4.5V input voltage. Low external-part count (one flying capacitor and two small bypass capacitors) makes the AIC1848 ideal for small, batterypowered applications.
1.8MHz Switching Frequency Short-Circuit and Over Temperature Protection Low Profile Package: SOT-23-6
The AIC1848 operates as a constant frequency mode switched capacitor voltage doubler to
APPLICATIONS
White LEDs Backlighting SIM Interface Supplies for Cellular Telephones Li-Ion Battery Backup Supplies Local 3V to 5V Conversion Smart Card Readers PCMCIA Local 5V Supplies
produce a regulated output and features with thermal shutdown capability and short circuit protection.
The AIC1848 is available in a space-saving
TYPICAL APPLICATION CIRCUIT
1-Cell Li-ion Battery
CIN 1F
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U1 1 VOUT GND 2 3 SHDN AIC1848
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C+ 6 5 4 C-
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SOT-23-6 package.
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VOUT R1
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COUT 1F
R2
R3
VIN
CFLY 1F
Regulated 5V Output from 2.7V to 4.5V Input WLED series number: NSPW310BS, VF=3.6V, IF=20mA
VOUT - V F IF
CIN, CFLY, COUT: JMK107BJ105KA, TAIYO YUDEN
Analog Integrations Corporation
Si-Soft Research Center TEL: 886-3-5772500 FAX: 886-3-5772510
3A1, No.1, Li-Hsin Rd. I , Science Park , Hsinchu 300, Taiwan , R.O.C.
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DS-1848P-01 030105
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AIC1848
ORDERING INFORMATION
AIC1848-XXXX PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE G: SOT-23-6 C: COMMERCIAL P: LEAD FREE COMMERCIAL Example: AIC1848CGTR in SOT-23-6 Package & Taping & Reel Packing Type AIC1848PGTR in Lead Free SOT-23-6 Package & Taping & Reel Packing Type PIN CONFIGURATION
SOT-23-6 TOP VIEW
C+ VIN 6 5 C4
(MARK SIDE) 1 2 3
VOUT GND SHDN
SOT-23-6 Marking
Part No. AIC1848CG Marking BP50 Part No. AIC1848PG Marking BP50P
ABSOLUATE MAXIMUM RATINGS
VIN to GND VOUT to GND All Other Pins to GND VOUT Short-Circuit Duration Operating Temperature Range Maximum Junction Temperature Storage Temperature Range Lead Temperature (Sordering 10 Sec.) 6V 6V 6V Continuous -40C to 85 C 125C -65C to 150 C 260C
Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
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AIC1848
TEST CIRCUIT
VOUT VIN CIN 1F
U1 1 VOUT 2 3 GND SHDN AIC1848 C+ 6 VIN C5 4
COUT 1F
CFLY 1F
ELECTRICAL CHARACTERISTICS
(TA=25C, CFLY=1F, CIN=1F, COUT=1F, unless otherwise specified.) (Note 1) PARAMETER Input Voltage 2.7V VIN< 4.5V, IOUT 40mA 3.1V VIN 4.5V, IOUT 100mA 2.7V VIN 5.0V, IOUT=0 , SHDN =VIN 2.7V VIN 5.0V, IOUT=0 , SHDN =0V VIN =2.7V , IOUT=30mA Oscillator Free Running High Low
SHDN =VIN SHDN = 0V
TEST CONDITIONS
SYMBOL VIN
MIN. 2.7 4.8
TYP.
MAX. 4.5
UNIT V
5 5 3 0.01 85 1.8
5.2 V 5.2 5 1.0 mA A % MHz V 0.3 V A A S mA
Output Voltage
VOUT 4.8 ICC I SHDN fOSC VIH VIL IIH IIL tON ISC -1 -1 50 300 1.4 1
Supply Current Shutdown Current Efficiency Switching Frequency Shutdown Input Threshold
Shutdown Input Current Vout Turn On Time Output Short Circuit Current
1 1
VIN =3V, IOUT = 1mA VIN=3V, VOUT= 0V, SHDN = VIN
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).
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AIC1848
TYPICAL PERFORMANCE CHARACTERISTICS
5.15 5.2
CIN= COUT=CFLY=1F
5.10
Output Voltage (V)
5.05
Output Voltage (V)
TA = -40C
TA =85C
TA=25C
5.1
VIN=3.2V
5.00
TA =25C
5.0
VIN=3V
4.95
IOUT=20mA
4.90 4.85 2.7 3.0 3.3 3.6 3.9 4.2 4.5
4.9
CIN=COUT=CFLY=1F
4.8 0
VIN=2.7V
50
100
150
200
Supply Voltage (V) Fig. 1 Output Voltage vs. Supply Voltage Fig. 2
Load Current (mA) Output Voltage vs. Load Current
3.0
2.0
TA=25C
Oscillator Frequency (MHz)
Supply Current (mA)
2.5
1.9
TA=-40C
2.0
1.8
TA = -40C
1.7
1.5
TA=85C CIN= COUT=CFLY=1F VSHDN=VIN
TA =25C
1.6
1.0 2.7 3.0 3.3 3.6 3.9 4.2 4.5
TA =85C
1.5 2.7 3.0 3.3 3.6 3.9 4.2 4.5
Supply Voltage (V) Fig. 3 No Load Supply Current vs. Supply Voltage
Supply Voltage (V) Fig. 4 Oscillator Frequency vs. Supply Voltage
3.0
800
Output Short Circuit Current (mA)
Shutdown Threshold Voltage (V)
CIN= COUT=CFLY=1F TA=25C VOUT=0V
600
2.5
TA=-40C TA=25C
2.0
TA=85C
1.5
400
1.0 2.7 3.0 3.3 3.6 3.9 4.2 4.5
200 2.7 3.0 3.3 3.6 3.9 4.2 4.5
Supply Voltage (V) Fig. 5 VSHDN Threshold Voltage vs. Supply Voltage Fig. 6
Supply Voltage (V) Short Circuit Current vs. Supply Voltage
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AIC1848
TYPICAL PERFORMANCE CHARACTERISTICS (Continued)
90 Vin=2.7 80 70 Vin=3.0V Vin=3.4V
90 Vin=2.7V 80 70 Vin=3.0V Vin=3.4V Vin=3.7V 60 50 40
CIN= COUT=1uF CFLY=1uF
Efficiency (%)
60 Vin=4.2V 50 40 30 20 1 10 100 1000
Efficiency (%)
Vin=3.7V
Vin=4.2V
30 20 1 10 100
CIN= COUT=1uF CFLY=0.1uF 1000
Load Current (mA)
Load Current (mA)
Fig.7 Efficiency vs. Load Current
Fig.8 Efficiency vs. Load Current
140 120 100 80 60 40 20 0
80
CIN=COUT=1F CFLY=0.1F
VIN=4.2V
Output Ripple Voltage (mV)
Output Ripple Voltage (mV)
70 60 50 40 30 20 10 0
VIN=3V CFLY=0.1F COUT=1uF
VIN=3.6V
VIN=3.0V
COUT=2.2uF
VIN=2.7V
0
50
100
150
200
250
0
20
40
60
80
100
120
Output Current (mA) Fig. 9 Output Ripple Voltage vs. Output Current
Output Current (mA) Fig. 10 Output Ripple Voltage vs. Output Current
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AIC1848
BLOCK DIAGRAM
VOUT 2 COUT 1F 1 VIN Control COMP CVREF SHDN 1 2 CFLY
1F
C+
CIN 1F
PIN DESCRIPTIONS
PIN 1:VOUT Regulated output voltage. For the best performance, VOUT should be bypassed a 1F (min.) low ESR capacitor with the shortest distance in between. Ground. Should be tied to ground plane direct for best performance.
SHDN pin is not allowed to float.
PIN 4: C-
-
Flying capacitor negative terminal. Input supply voltage. VIN should be bypassed a 1F (min.) low ESR capacitor with the shortest distance in between. Flying capacitor positive terminal.
PIN 5: VIN -
PIN 2: GND -
PIN 3: SHDN - Active low shutdown input. Tie to higher than 1.4V to enable device, 0.3V or less to disable device.
PIN 6: C+
-
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AIC1848
APPLICATION INFORMATION
Introduction
AIC1848 is a micropower charge pump DC/DC converter that produces a regulated 5V output with an input voltage range from 2.7V to 4.5V. It utilizes the charge pump topology to boost VIN to a regulated output voltage. Regulation is obtained by sensing the output voltage through an internal resistor divider. A switched doubling circuit enables the charge pump when the feedback voltage is lower than the internal comparator point, and vice versa. When the charge pump is enabled, a two-phase non-overlapping clock activates the charge pump switches. IC junction temperature increased. When the temperature of device exceeds 150C, the thermal protection will shut the switching down and the temperature will reduce afterwards. Once the temperature drops below 135C, the charge pump switching circuit will re-start. If the fault doesn't eliminate, the above protecting operation will repeat again and again. It allows AIC1848 to continuously work at short circuit condition without damaging the device.
Shutdown
In shutdown mode, the output is disconnected from input. The input current gets extremely low since most of the circuitry is turned off. Due to high impedance, shutdown pin can't be floated.
Operation
This kind of converter uses capacitors to store and transfer energy. Since the capacitors can't change to the voltage level abruptly, the voltage ratio of VOUT to VIN is limited. Capacitive voltage conversion is obtained by switching a capacitor periodically. Refer to Fig. 11, during the on state of internal clock, Q1 and Q4 are closed, which charges CFLY to VIN level. During the off state, Q3 and Q2 are closed. The output voltage is VIN plus VCFLY, that is, 2VIN.
VIN CIN Q3 Q1 CFLY Q4 Q2 VOUT COUT
Efficiency
Refer to Fig. 12 and Fig. 13, they shows the circuit of charge pump at different operation states. RDS-ON is the resistance of the switching element at conduction. ESR is the equivalent series resistance of the flying capacitor CFLY. ION-AVE and IOFF-AVE are the average current during on state and off state, respectively. D is the duty cycle, which means the proportion the on state takes. Let's take advantage of conversation of charge for capacitor CFLY. Assume that the capacitor CFLY has reached its steady state. The amount of charge flowing into CFLY during on state is equal to that flowing out of CFLY at off state.
ION- AVE x DT = IOFF - AVE x (1 - D)T ION- AVE x D = IOFF - AVE x (1 - D)
Fig. 11 The circuit of charge pump
Short Circuit/Thermal Protection
AIC1848 obtains built-in short circuit current limiting and over temperature protection. During the short circuit condition, the output current is automatically constrained at approximately 300mA. Continued current limit will cause internal
(1) (2)
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AIC1848
IIN = ION- AVE x D + IOFF- AVE x (1 - D) = 2 x ION- AVE x D = 2 x IOFF- AVE x (1 - D) IOUT = IOFF- AVE x (1 - D) IIN = 2 x IOUT
External Capacitor Selection
(3) Three external capacitors, CIN, COUT and CFLY, determine AIC1848 performances. Optimum performance can be obtained by using low ESR ceramic capacitors. Due to high ESR, tantalum (4) and aluminum capacitors are not recommended for charge pump application.
For AIC1848, the controller takes the PWM (Pulse Width Modulation) control strategy. When the duty cycle is limited to 0.5, there will be:
ION- AVE x 0.5 x T = IOFF- AVE x (1 - 0.5) x T ION- AVE = IOFF- AVE
To reduce noise and ripple, low ESR ceramic capacitor is recommended for CIN and COUT. The value of COUT determines the amount of output ripple voltage. An output capacitor with larger value results in smaller ripple. CFLY is critical for the charge pump. The larger CFLY is, the larger output current and smaller ripple voltage obtain. However, large CIN and COUT are required when large CFLY applies. The ratio of CIN (as well as COUT) to CFLY should be approximately 10:1.
According to the equation (4), we know that as long as the flying capacitor CFLY is at steady state, input current is double of output current. The efficiency of charge pump is given below:
V V V xI xI = OUT OUT = OUT OUT = OUT VIN x IIN VIN x 2IOUT 2VIN
VIN
CIN
ION RDS-ON-Q1 ESR CFLY Q3 RDS-ON-Q4 Q2
VOUT COUT
Layout Considerations
Due to the switching frequency and high transient current of AIC1848, careful consideration of PCB layout is necessary. To achieve the best performance of AIC1848, minimize the distance between minimize every every two components length and also a
Fig. 12 The on state of charge pump circuit
connection
with
maximum trace width. Make sure each device
VIN Q1 CIN RDS-ON-Q3
IOFF
RDS-ON-Q2 ESR CFLY Q4
VOUT COUT
connects to immediate ground plane. Fig. 14 to Fig. 16 show the recommended layout.
Fig. 13 The off state of charge pump circuit
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AIC1848
Fig. 14 Top layer
Fig. 15 Bottom layer
Fig. 16 Top-over layer
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AIC1848
APPLICATION EXAMPLES
VIN CIN 1F 1 2 3 VOUT GND SHDN U1 CAP+ VIN CAPAIC1848 6 5 4 CFLY1 0.1F VOUT COUT 1F
1 VOUT 2 GND VSHDN 3 SHDN U2
CAP+ VIN CAP-
6 5 4 CFLY2 0.1F
AIC1848
Fig. 17 Parallel Two AIC1848 to Obtain the Regulated 5V Output with large output current.
5Vout Vin CIN 1uF 1 2 3 U1 VOUT GND SHDN AIC1848 Flash Control C+ VIN CCOUT 1uF R1 27 R2 9.1 Q1 Si2302
6 5 4 CFLY 0.1uF
Enable
Fig. 18 Flash WLED Application
Vin Cin 1uF 1 2 3 5Vout U1 VOUT GND SHDN AIC1848 R3 1k 1 2 3 U2 VOUT GND SHDN AIC1848 Flash R4 1M C+ VIN C6 5 4 CFLY2 0.1uF C+ VIN C6 5 4 CFLY1 0.1uF Cout 1uF R1 27 R2 2.7 Q1 Si2302
Enable
C1 0.1uF
Fig. 19 Flash WLED Application with Parallel Two AIC1848
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AIC1848
PHYSICAL DIMENSIONS (unit: mm)
SOT-23-6
D
S Y M B O L
SOT-26 MILLIMETERS MIN. 0.95 0.05 0.90 0.30 0.08 2.80 2.60 1.50 0.95 BSC 1.90 BSC 0.30 0.60 REF 0 8 0.60 MAX. 1.45 0.15 1.30 0.50 0.22 3.00 3.00 1.70
A
E1
A1
E
A2 b c
A
A
e e1
SEE VIEW B
D E E1
b A2
WITH PLATING
e e1
A
c
BASE METAL SECTION A-A
L L1
A1
0.25 L L1
VIEW B GAUGE PLANE SEATING PLANE
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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