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FEATURES
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wInput Range: 2.7V to 5.0V
No Inductors Needed
at .D Output Current: 100mA (V w 110mA (V
Ultralow Power: IIN = 13A Regulated 5V 4% Output Voltage
IN =3.3V) IN =3.6V)
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AIC1845
Regulated 5V Charge Pump In SOT-23
DESCRIPTION
The AIC1845 is a micropower charge pump DC/DC converter that produces a regulated 5V output. The input voltage range is 2.7V to 5.0V. Extremely low operating current (13A typical with no load) and a low external-part count (one 0.22F flying capacitor and two small bypass capacitors at VIN and VOUT ) make the AIC1845 ideally suitable for small, battery-powered applications.
Very Low Shutdown Current: <1A Internal Oscillator: 650KHz Short-Circuit and Overtemperature Protection 6-Pin SOT-23 Package
The AIC1845 operates as a PSM (Pulse Skipping Modulation) mode switched capacitor
APPLICATIONS
White or Blue LED Backlighting SIM Interface Supplies for Cellular Telephones Li-Ion Battery Backup Supplies Local 3V to 5V Conversion Smart Card Readers PCMCIA Local 5V Supplies
voltage doubler to produce a regulated output and features with thermal shutdown capability and short circuit protection. The AIC1845 is available in a 6-pin SOT-23 package.
TYPICAL APPLICATION CIRCUIT
1-Cell Li-ion Battery
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* ** CFLY
CIN 2.2F
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U1 1 VOUT GND SHDN AIC1845 2 3
S a
C+ 6 5 4 C-
e h
U t4 e
VOUT
.c
m o
** R1
COUT 2.2F
*
*
*
*
VIN
0.22F CFLY
Regulated 5V Output from 2.7V to 5.0V Input WLED series number: NSPW310BS, VF=3.6V, IF=20mA
R1 = VOUT - VF , NWLED: The number of WLED IF x N WLED
CIN, COUT: CELMK212BJ225MG (X5R) (0805), TAIYO YUDEN : CEEMK212BJ224KG (X7R) (0805), 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-1845P-03 010405
1
AIC1845
ORDERING INFORMATION
AIC1845XXXX PACKING TYPE TR: TAPE & REEL BG: BAG PACKAGE TYPE G: SOT-23-6 C: COMMERCIAL P: LEAD FREE COMMERCIAL Example: AIC1845CGTR in SOT-23-6 Package & Taping & Reel Packing Type AIC1845PGTR 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. AIC1845CG AIC1845PG Marking BO50 BO50P
ABSOLUATE MAXIMUM RATINGS
VIN to GND VOUT to GND All Other Pins to GND VOUT Short-Circuit Duration Operating Temperature Range 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.
TEST CIRCUIT
Refer to TYPICAL APPLICATION CIRCUIT.
2
AIC1845
ELECTRICAL CHARACTERISTICS
(TA=25C, CFLY=0.22F, CIN=2.2F, COUT=2.2F, unless otherwise specified.) (Note 1)
PARAMETER Input Voltage 2.7V VIN< 3.3V, IOUT 30mA 3.3V VIN 5.0V, IOUT 60mA VIN=3V, VOUT=5.0V SHDN =VIN 2.7V VIN 5.0V, IOUT=0 , SHDN =VIN 2.7V VIN 5.0V, IOUT=0 , SHDN =0V VIN =3V , IOUT=50mA VIN =2.7V , IOUT=30mA Oscillator Free Running TEST CONDITIONS SYMBOL VIN MIN. 2.7 4.8 VOUT 4.8 5.0 5.2 mA 13 0.01 60 83 650 1.4 0.3 -1 -1 0.5 170 1 1 30 1.0 A A mV % KHz V V A A mS mA 5.0 TYP. MAX. 5.0 5.2 V UNIT V
Output Voltage
Continuous Output Current Supply Current Shutdown Current Output Ripple Efficiency Switching Frequency Shutdown Input Threshold (High) Shutdown Input Threshold (Low) Shutdown Input Current (High) Shutdown Input Current (Low) Vout Turn On Time Output Short Circuit Current
IOUT
ICC I SHDN VR fOSC VIH VIL
60
SHDN =VIN SHDN = 0V
IIH IIL tON ISC
VIN =3V, IOUT = 0mA VIN=3V, VOUT= 0V, SHDN = VIN
Note1: 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).
3
AIC1845
TYPICAL PERFORMANCE CHARACTERISTICS
(CIN, COUT: CELMK212BJ225MG, CFLY: CEEMK212BJ224KG)
5.15 5.10 IOUT=25mA
20
Supply Current ()
Output Voltage (V)
5.05 5.00 4.95 4.90 4.85 2.5
COUT=10F CFLY=1F TA = -40C TA =25C TA =85C
TA=-40C
15
TA=25C
10
TA=85C
IOUT=0A CFLY=1F VSHDN=VIN
5 2.5 3.0 3.5 4.0 4.5 5.0
3.0
3.5
4.0
4.5
5.0
Supply Voltage (V) Fig. 1 Line Regulation
5.15 5.10 TA=25C COUT=10F CFLY=1F VIN=3.6V
Supply Voltage (V) Fig. 2 No Load Supply Current vs. Supply Voltage
5.2 5.1
Output Voltage (V)
Output Voltage (V)
5.05 5.00 4.95 4.90 VIN=2.7V 4.85 0 20 40 VIN=3.0V 60 80 100 VIN=3.3V
5.0 4.9 4.8 4.7 4.6 4.5
VIN=3.3V VIN=3.6V TA=25C CFLY=0.22F COUT=2.2F
0 10 20 30 40
VIN=2.7V
50 60 70 80
VIN=3.0V
90 100 110 120 130
120
140
160
Output Current (mA) Fig. 3 Load Regulation
100 90 80
100
Output Current (mA) Fig. 4 Load Regulation
CT=25C CFLY=1F
VIN=2.7V
90 80 70 60 50 40 30 0.01
VIN=2.7V
VIN=3.0V
Efficiency (%)
60
50 40 30 20 10
VIN=3.0V VIN=3.3V VIN=3.6V
Efficiency (%)
70
VIN=3.3V
VIN=3.6V
TA=25C CFLY=0.22F
0.1 1 10 100
0
0.001
0.01
0.1
1
10
100
Output Current (mA) Fig. 5 Efficiency
Output Current (mA) Fig. 6 Efficiency
4
AIC1845
TYPICAL PERFORMANCE CHARACTERISTICS
50 45 40 175 150
(Continued)
Output Ripple (mV)
Output Ripple (mV)
35 30 25 20 15 10
125
VIN=3.6V
VIN=3.6V
100 75
VIN=3.3V VIN=3.0V VIN=2.7V 0 20
40 60 80
VIN=3.3V
50 25
COUT=10F CFLY=1F
100 120 140
VIN=3.0V VIN=2.7V
0 20 40 60 80
COUT=2.2F CFLY=0.22F
100 120 140
5
0
0
Output Current (mA) Fig.7 Output Current vs. Output Ripple
Output Current (mA)
Fig. 8 Output Current vs. Output Ripple
1000
5.05
900
VIN=2.5V
800
Output Voltage (V)
Frequency (KHz)
5.00
700
4.95
VIN=3.0V CFLY=1F IOUT=50mA
600
4.90
500
400
-60
-40
-20
0
20
40
60
80
100
120
140
Temperature (C) Fig. 9 Frequency vs. Temperature
280
4.85 -60
-40
-20
0
20
40
60
80
100
120
140
Fig. 10
Temperature (C) Output Voltage vs. Temperature
Short-Circuit Current (mA)
Short-Circuit Current (mA)
260 240 220 200 180 160 140 120 100 2.5
TA=25C CFLY=1F
220 200 180 160 140 120 100
TA=25C CFLY=0.22F
2.5 3.0 3.5 4.0 4.5 5.0 5.5
3.0
3.5
4.0
4.5
5.0
Supply Voltage (V) Fig. 11 Short-Circuit Current vs. Supply Voltage
Supply Voltage (V) Fig. 12 Short-Circuit Current vs. Supply Voltage
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AIC1845
TYPICAL PERFORMANCE CHARACTERISTICS
CN
(Continued)
CN
VOUT VOUT
Fig. 13
Output Ripple
VIN=3.0V, IOUT=50mA, COUT=10F,CFLY=1F
Fig. 14 Output Ripple VIN=3.0V, IOUT=50mA, COUT=2.2F, CFLY=0.22F
IOUT
VOUT
VOUT
IOUT
Fig. 15 Load Transient Response VIN=3.0V, IOUT=0mA~50mA,COUT=10F, CFLY=1F
Fig. 16 Load Transient Response VIN=3.0V, IOUT=0mA~50mA,COUT=2.2F, CFY=0.22F
VOUT
VOUT
V SHDN
V SHDN
Fig. 17 Start-Up Time VIN=3.0V, IOUT=0A, COUT=10F
Fig. 18 Start-Up Time VIN=3.0V, IOUT=0A, COUT=2.2F
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AIC1845
BLOCK DIAGRAM
VOUT 2 COUT 2.2F 1 VIN Control COMP CVREF SHDN 1 2 CFLY
0.22F
C+
CIN 2.2F
PIN DESCRIPTIONS
PIN 1:VOUT Regulated output voltage. For the best performance, VOUT should be bypassed with a 2.2F (min) low ESR capacitor with the shortest distance in between. Ground. Should be tied to a ground plane for best performance. AIC1845. SHDN is not allowed to float. PIN 4: CPIN 5: VIN Flying capacitor negative terminal. Input supply voltage. VIN should be bypassed with a 2.2F (min) low ESR capacitor. Flying capacitor positive terminal.
PIN 2: GND -
PIN 3: SHDN - Active low shutdown input. A low voltage on SHDN disables the
PIN 6: C+
-
7
AIC1845
APPLICATION INFORMATION
Introduction
AIC1845 is a micropower charge pump DC/DC converter that produces a regulated 5V output with an input voltage range from 2.7V to 5.0V. 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 trip point of the internal comparator, and vice versa. When the charge pump is enabled, a two-phase non-overlapping clock activates the charge pump switches. To maximize battery life for a battery-used application, quiescent current is limited up to 13A.
Short Circuit/Thermal Protection
AIC1845 owns a built-in short circuit current limiting as well as an over temperature protection. During the short circuit condition, the output current is automatically constrained at approximately 170mA. This short circuit current will cause a rise in the internal IC junction temperature. When the die temperature exceeds 150C, the thermal protection will shut the charge pump switching operation down and the die temperature will reduce afterwards. Once the die 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 AIC1845 to continuously work at short circuit condition without damaging the device.
Operation
This kind of converter uses capacitors to store and transfer energy. Since the capacitors can't change their voltage level abruptly, the voltage ratio of VOUT over VIN is limited to some range. Capacitive voltage conversion is obtained by switching a capacitor periodically. It first charges the capacitor by connecting it across a voltage source and then connects it to the output. Referring to Fig. 19, during the on state of internal clock, Q1 and Q4 are closed, which charges C1 to VIN level. During the off state, Q3 and Q2 are closed. The output voltage is VIN plus VC1, that is, 2VIN.
VIN CIN Q3 Q1 C1 Q4 Q2 VOUT COUT
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.
Efficiency
Referring to Fig. 20 and Fig. 21 here shows the circuit of charge pump at different states of operation. RDS-ON is the resistance of the switching element at conduction. ESR is the equivalent series resistance of the flying capacitor C1. IONAVE
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 C1. Assume that the capacitor C1 has reached its steady state. The amount of charge flowing into C1 during on state is equal to that flowing out of C1 at off state.
Fig. 19 The circuit of charge pump
8
AIC1845
ION- AVE x DT = IOFF - AVE x (1 - D)T ION- AVE x D = IOFF - AVE x (1 - D)
(1) (2)
External Capacitor Selection
Three external capacitors, CIN, COUT and CFLY, determine AIC1845 performances, in the aspects of output ripple voltage, charge pump strength and transient. Optimum performance can be obtained by the use of ceramic capacitors with low ESR. Due to high ESR, capacitors of tantalum and aluminum are not recommended for charge pump application. To reduce noise and ripple, a low ESR ceramic capacitor, ranging from 2.2F to 10F, is recommended for CIN and COUT. The value of COUT determines the amount of output ripple voltage. An output capacitor with larger value ..........(5) results in smaller ripple. CFLY is critical for the strength of charge pump. The larger CFLY is, the larger output current and smaller ripple voltage obtain. However, large CIN and COUT are expected when a large ....FLY ..(6) C .... applies. The ratio of CIN (as well as COUT) to CFLY should be approximately 10:1. The value of capacitors, which is used under operation conditioin, determines the performance of a charge pump converter. And two factors, as follows, affect the capacitance of capacitor. 1. Material: Ceramic capacitors of different materials, such as X7R, X5R, Z5U and Y5V, have different tolerance in temperature and differnet cpacitance loss. For example, a X7R or X5R type of capacitor can retain most of the capacitance at temperature from -40C to 85C, but a Z5U or Y5V type will lose most of the capacitance at that temperature range.
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 = 2IOUT
(3)
For AIC1845, the controller takes the PSM (Pulse Skipping 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
According to the equation (4), we know that as long as the flying capacitor C1 is at steady state, the input current is twice the 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 Q3
Q1 ESR C1
Q2
VOUT COUT
Q4
RDS-ON
Fig. 20 The on state of charge pump circuit
VIN CIN
RDS-ON Q1 Q3 RDS-ON
IOFF
Q2
VOUT COUT
ESR Q4 C1
Fig. 21 The off state of charge pump circuit
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AIC1845
2. Package Size: A ceramic capacitor with large volume (0805), gets a lower ESR than a small one (0603). Therefore, large devices can improve more transient response than small ones. Table 1 lists the recommended components for AIC1845 application. Table.1 Bill of Material
Designator Part Type Description Vendor Phone
2 PESR IOUT x ESR x 2 = IOUT x 4ESR
switching element is
2 PRDS -ON IOUT x
2 x RDS - ON 0.5(1 - 0.5)
2 = IOUT x 8R DS - ON
1 0.5(1 - 0.5)
In fact, no matter the current is at on state or off state, it decays exponentially rather than flows steadily. And the root mean square value of exponential decay is not equal to that of steady flow. That is why the approximation comes from. Let's treat the charge pump circuit in another
CIN
2.2
CELMK212BJ225MG (X5R) CEEMK212BJ -224KG (X7R) CELMK212BJ225MG (X5R)
TAIYO YUDEN TAIYO YUDEN TAIYO YUDEN
(02) 27972155~9
CFLY
0.22
(02) 27972155~9
COUT
2.2
(02) 27972155~9
approach and lay the focus on the flying capacitor C1. Referring to Fig. 20, when the circuit is at the on state, the voltage across C1 is:
VC-ON (t) = VIN - 2R DS-ON x ION (t) - ESR x ION (t) ...(9)
Power Dissipation
Let's consider the power dissipation of RDS-ON and ESR. Assume that the RDS-ON of each internal switching element in AIC1845 is equal and ESR is the equivalent series resistance of CFLY (ref to Fig. 20 and Fig. 21). The approximation of the power loss of RDS-ON and ESR are given below:
PRDS-ON
2 ION- AVE 2 x 2RDS - ON x D + IOFF - AVE
The average of VC1 during the on state is:
VC-ON- AVE = VIN - 2R DS-ON x ION- AVE - ESR x ION- AVE ............................(10)
Similarly, referring to Fig. 21, when the circuit is at the off state, the voltage of C1 is:
VC-OFF (t) = VOUT - VIN + 2R DS-ON x IOFF (t) + ESR x IOFF (t) .................................(11)
x 2RDS - ON x (1 - D)
IIN 2 I ) x 2RDS- ON x D + ( OUT )2 x 2RDS- ON x (1 - D) 2D 1- D 2IOUT 2 I =( ) x 2RDS -ON x D + ( OUT )2 x 2RDS -ON x (1 - D) 2D 1- D 2 2 2 2 = IOUT x ( RDS- ON ) + IOUT x ( RDS -ON ) D 1- D 2 2 = IOUT x x RDS -ON D(1 - D) =(
The average of VC1 during the off state is:
VC-OFF- AVE = VOUT - VIN + 2R DS-ON x IOFF- AVE .......... (7) OFF- AVE + ESR x I ....................(12)
2 2 PESR ION- AVE x ESR x D + IOFF- AVE x ESR x (1 - D)
I IIN 2 ) x ESR x D + ( OUT ) 2 x ESR x (1 - D) 2D 1- D 12 1 2 = IOUT x ESR x + IOUT x ESR x D 1- D 1 2 = IOUT x ESR x D(1 - D) When the duty cycle is 0.5, the power loss of =(
The difference of charge stored in C1 between on state and off state is the net charge transferred to the output in one cycle.
10
AIC1845
Q = Q ON - Q OFF = C1 x (VC1-ON- AVE - VC1-OFF - AVE ) = C1 x (2VIN - VOUT - 2R DS-ON x ION- AVE - 2R DS-ON x IOFF- AVE - ESR x ION- AVE - ESR x IOFF- AVE ) = C1 x (2VIN - VOUT - 2R DS -ON x = C1 x [2VIN - VOUT - (2R DS-ON I I I IOUT - 2R DS -ON x OUT - ESR x OUT - ESR x OUT ) 1- D D 1- D D 1 + ESR) x IOUT x ] D(1 - D)
.........(13)
Thus the output current can be written as
IOUT = f x Q = f x (Q ON - Q OFF ) = f x C1 x [2VIN - VOUT - (2R DS-ON + ESR ) x IOUT x 1 ] D(1 - D)
(14)
When the duty cycle is 0.5, the output current can be written as:
IOUT = f x C1 x [2VIN - VOUT - (2R DS-ON + ESR) x IOUT x = fC1 x [2VIN - VOUT - (8R DS-ON + 4ESR) x IOUT ] 1 ] 0.5(1 - 0.5)
(15)
And equation (15) can be re-written as:
2VIN - VOUT = 1 x IOUT + (8R DS-ON + 4ESR) x IOUT fC1
(16)
According the equation (16), when the duty cycle is 0.5, the equivalent circuit of charge pump is shown in Fig. 22. The term 8RDS-ON is the total effect of switching resistance, 1/fC1 is the effect of flying capacitor and 4ESR is its equivalent resistance. From the equivalent circuit shown in Fig. 22, it is seen that the terms 1/fC1, 4ESR and 8RDS-ON should be as small as possible to get large output current. However, for users, since the RDS-ON is fixed and manufactured in IC, what we can do is to lower 1/fC1 and ESR. However even the effect of 1/fC1 and ESR can be kept as small as possible, the term 8RDS-ON still dominates the role that limits the maximum output current.
2VIN 1/fC1
IOUT 8RDS-ON 4ESR COUT
VOUT LOAD
Fig. 22 The euqivalent circuit of charge pump
Layout Considerations
Due to the switching frequency and high transient current of AIC1845, careful consideration of PCB layout is necessary. To achieve the best performance of AIC1845, minimize the distance between minimize every every two components length and also a connection with
maximum trace width. Make sure each device connects to immediate ground plane. Fig. 23 to Fig. 25 show the recommended layout.
11
AIC1845
Fig. 23 Top layer
Fig. 24 Bottom layer
Fig. 25 Topover layer
APPLICATION EXAMPLES
VIN CIN 2.2 1 2 3 VOUT GND SHDN U1 CAP+ VIN CAPAIC1845 6 5 4 CFLY1 0.22F VOUT COUT 2.2F
1 VOUT 2 GND VSHDN 3 SHDN U2
CAP+ VIN CAP-
6 5 4 CFLY2 0.22F
AIC1845
CIN, COUT : TAIYO YUDEN Ceramic Capacitor, CELMK212BJ225MG (X5R) (0805) CFLY1, CFLY2: TAIYO YUDEN Ceramic Capacitor, CEEMK212BJ224KG (X7R) (0805)
Fig. 26 Parallel Two AIC1845 to Obtain the Regulated 5V Output with large output current.
USB CIN 2.2F 1 2 3 VSHDN VOUT GND SHDN U1 CAP+ VIN CAPAIC1845 6 5 4 CFLY 0.22F
VOUT COUT 2.2F
CIN, COUT: TAIYO YUDEN Ceramic Capacitor, CELMK212BJ225MG (X5R) (0805) : TAIYO YUDEN Ceramic Capacitor, CEEMK212BJ224KG (X7R) (0805) CFLY1
Fig. 27 Regulated 5V from USB
12
AIC1845
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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