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Positive Doubling Charge Pump with Shutdown in SOT Package TC1240 TC1240
Positive Doubling Charge Pump with Shutdown in SOT Package
FEATURES
s s s s s s s s s Space Saving 6-Pin SOT-23A Package >99% Typical Voltage Conversion Efficiency Voltage Doubling Operates from +2.5V to +4.0V Low Output Resistance (17 Typical) Only Two External Capacitors Required Consumes 180A (Typical) in Active Mode Power-Saving Shutdown Mode (1A Maximum) Fully Compliant with 1.8V Logic Sytems
GENERAL DESCRIPTION
The TC1240 is a doubling CMOS charge-pump voltage converter in a small 6-Pin SOT-23A package. TC1240 doubles an input voltage which can range from +2.5V to +4.0V. Conversion efficiency is typically >99%. Internal oscillator frequency is 160kHz for the TC1240. The TC1240 has an active high shutdown which limits the current consumption of the device to less than 1A. External component requirement is only two capacitors for standard voltage doubler applications. All other circuitry, including control, oscillator, power MOSFETs are integrated on-chip. Typical supply current is 180A and the device is available in a 6-Pin SOT-23A surface mount package.
APPLICATIONS
s s s s s Cellular Phones Pagers PDAs, Portable Dataloggers Battery-Powered Devices Handheld Instruments
ORDERING INFORMATION
Part Number TC1240ECH Package 6-Pin SOT-23A Temp. Range -40C to +85C
TYPICAL OPERATING CIRCUIT
PIN CONFIGURATION
Positive Voltage Doubler
6-Pin SOT-23A
C+ C 1 C- SHDN TC1240
ON OFF
VIN
INPUT
VIN 1 6 C+
GND 2
TC1240ECH
5
OUT
OUT GND C2
2 x INPUT
C-
3
4
SHDN
NOTE: *6-Pin SOT-23A is equivalent to EIAJ SC-74
TC1240-1 7/7/00
TelCom Semiconductor reserves the right to make changes in the circuitry and specifications of its devices. 1
Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
ABSOLUTE MAXIMUM RATINGS*
Input Voltage (VIN to GND) .......................... +4.5V, -0.3V Output Voltage (OUT to GND) .............. +9.0V, VIN - 0.3V Current at OUT Pin ................................................. 50 mA Short-Circuit Duration -OUT to GND ................ Indefinite Operating Temperature Range ...............-40 C to +85C Power Dissipation (TA 70C) 6-Pin SOT-23A ..........................................240 mW Storage Temperature (Unbiased) ......... -65 C to +150C Lead Temperature (Soldering, 10 sec) ................. +300C
*Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS: TA = -40 to +85 C, VIN = +2.8V, C1 = C2 = 3.3F , SHDN = GND,
unless otherwise noted. Typical values are at TA = +25C.
Symbol IDD ISHDN VMIN VMAX FOSC FSW VIH VIL PEFF VEFF ROUT Parameter Supply Current Shutdown Supply Current Minimum Supply Voltage Maximum Supply Voltage Oscillator Frequency Switching Frequency Shutdown Input Logic High Shutdown Input Logic Low Power Efficiency Voltage Conversion Efficiency Output Resistance (Note 1) Test Conditions RLOAD = SHDN = VIN RLOAD = 1.0K RLOAD = 1.0K TA = -40 C to +85C TA = -40 C to +85C VIN = VMIN to VMAX VIN = VMIN to VMAX RLOAD = 1.0K RLOAD = RLOAD = 1.0K TA = -40C to +85C Min -- -- 2.5 -- -- 40 1.4 -- 86 97.5 -- -- Typ 180 0.1 -- -- 160 80 -- -- 93 99.96 17 -- Max 300 1.0 -- 4.0 -- 125 -- 0.4 -- -- -- 30 Units A A V V kHz kHz V V % %
NOTE: 1. Capacitor contribution is approximately 26% of the output impedance [ESR = 1 / pump frequency x capacitance)]. 2. Switching frequency is one-half internal oscillator frequency.
PIN DESCRIPTION
Pin No. (6-Pin SOT-23A) 1 2 3 4 5 6 Symbol VIN GND C- SHDN OUT C+ Description Power Supply Input. Ground. Commutation Capacitor Negative Terminal. Shutdown Input (Active High). Doubled Output Voltage. Commutation Capacitor Positive Terminal.
TC1240-1 7/7/00
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Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
DETAILED DESCRIPTION
The TC1240 charge pump converter doubles the voltage applied to the VIN pin. Conversion consists of a twophase operation (Figure 1). During the first phase, switches S2 and S4 are open and S1 and S3 are closed. During this time, C1 charges to the voltage on VIN and load current is supplied from C2. During the second phase, S2 and S4 are closed, and S1 and S3 are open. During this second phase, C1 is level shifted upward by VIN volts. This connects C1 to the reservoir capacitor C2, allowing energy to be delivered to the output as needed. The actual voltage is slightly lower than 2 x VIN since the four switches (S1 - S4) have an on-resistance and the load drains charge from reservoir capacitor C2.
S2
(2) I2R losses due to the on-resistance of the MOSFET switches on-board the charge pump. (3) Charge pump capacitor losses due to effective series resistance (ESR). (4) Losses that occur during charge transfer (from commutation capacitor to the output capacitor) when a voltage difference between the two capacitors exists. Most of the conversion losses are due to factors (2) and (3) above. These losses are given by Equation 1(b). (a) PLOSS (2, 3) = IOUT 2 x ROUT (b) IOUT2 x
[(f
1
PUMP)
+8RSWITCH + 4ESRC1 + ESRC2 C1
Equation 1.
]
S1 VIN C1
TC1240 OUT = 2 x VIN C2
S3
S4
The pump frequency in Equation 1(b) is defined as onehalf the oscillator frequency (i.e. fPUMP = fOSC/2). The 1/(fPUMP)(C1) term in Equation 1(b) is the effective output resistance of an ideal switched capacitor circuit (Figures 2a, 2b). The value of RSWITCH can be approximated at 1.4 for the TC1240. The remaining losses in the circuit are due to factor (4) above, and are shown in Equation 2. The output voltage ripple is given by Equation 3. PLOSS(4) = [(0.5)(C1) (4VIN2- VOUT2 ) + (0.5)(C2)(2VOUT VRIPPLE - VRIPPLE2 )] x fOSC
Equation 2.
VIN
OSC
Figure 1. Ideal Swiched Capacitor Charge Pump Doubler
APPLICATIONS INFORMATION Output Voltage Considerations
TheTC1240 performs voltage doubling but does not provide regulation. The output voltage will droop in a linear manner with respect to load current. The value of this equivalent output resistance is approximately 17 nominal at +25C and VIN = +2.8V. VOUT is approximately +5.6V at light loads, and droops according to the equation below: VDROOP = IOUT x ROUT VOUT = 2 x VIN - VDROOP
V+
VRIPPLE = IOUT +2(IOUT)(ESRC2) (fOSC)(C2)
Equation 3.
f VOUT RL
C1
C2
Figure 2a. Ideal Swiched Capacitor Model
REQUIV V+ REQUIV =
1 f x C1
Charge Pump Efficiency
The overall power efficiency of the charge pump is affected by four factors: (1) Losses from power consumed by the internal oscillator, switch drive, etc. (which vary with input voltage, temperature and oscillator frequency).
TC1240-1 7/7/00
VOUT C2 RL
Figure 2b. Equivalent Output Resistance 3
Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
CAPACITOR SELECTION
In order to maintain the lowest output resistance and output ripple voltage, it is recommended that low ESR capacitors be used. Additionally, larger values of C1 will lower the output resistance and larger values of C2 will reduce output ripple. (See Equation 1(b)). Table 1 shows various values of C1 and the corresponding output resistance values @ +25C. It assumes a 0.1 ESRC1 and 1.2 RSW. Table 2 shows the output voltage ripple for various values of C2. The VRIPPLE values assume 5 mA output load current and 0.1 ESRC2. Table 1. Output Resistance vs. C1 (ESR = 0.1)
C1 (F) 0.47 1 2.2 3.3 4.7 10 47 100 TC1240 ROUT() 47 28.5 19.5 17 15.5 13.6 12.5 12.2
C3 VIN
VOUT 5 OUT C1+ C 6 C2 TC1240 1 VIN 3 -- C C1 4 SHDN GND 2 C1 RL
Device TC1240
C1 3.3F
C2 3.3F
C3 3.3F
Voltage Doubler
Figure 3. Test Circuit
VOLTAGE DOUBLER
The most common application for charge pump devices is the doubler (Figure 3). This application uses two external capacitors - C1 and C2 (plus a power supply bypass capacitor, if necessary). The output is equal to 2 x VIN minus any voltage drops due to loading. Refer to Table 1 and Table 2 for capacitor selection.
V
IN
Table 2. Output Voltage Ripple vs. C2 (ESR = 0.1) IOUT 5mA
C1 (F) 0.47 1 2.2 3.3 4.7 10 47 100 TC1240 VRIPPLE (mV) 142 67 30 20 14 6.7 2.5 1.6
6 C+ C1A 2 VIN 1 6 C1B C+ VIN 1
TC1240
GND 2 GND
TC1240
3 C- 4 SHDN
"1"
OUT
5 C2A
3 4
C- SHDN
"n"
OUT
5
VOUT
C2B
VOUT = (n + 1)VIN
Figure 4. Cascading Multiple Devies to Increase Output Voltage
INPUT SUPPLY BYPASSING
The VIN input should be capacitively bypassed to reduce AC impedance and minimize noise effects due to the switching internal to the device. The recommended capacitor should be a large value (at least equal to C1) connected from the input to GND.
CASCADING DEVICES
Two or more TC1240s can be cascaded to increase output voltage (Figure 4). If the output is lightly loaded, it will be close to ((n + 1) x VIN) but will droop at least by ROUT of the first device multiplied by the IQ of the second. It can be seen that the output resistance rises rapidly for multiple cascaded devices. For the case of the two-stage `tripler'output resistance can be approximated as ROUT = 2 x ROUT1 + ROUT2, where ROUT1 is the output resistance of the first stage, and ROUT2 is the output resistance of the second stage.
4
SHUTDOWN INPUT
TheTC1240 is disabled when SHDN is high, and enabled when SHDN is low. This input cannot be allowed to float.
TC1240-1 7/7/00
Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
ROUT = ROUT OF SINGLE DEVICE NUMBER OF DEVICES VIN 1 3 2 6 4 TC1240 C1B 3 TC1240 2 "n" 6 4 SHDN ... C2 Shutdown Control 5 ... 1 VIN
However, to preserve ripple performance the value of C2 should be scaled according to the number of paralleled TC1240s.
LAYOUT CONSIDERATIONS
As with any switching power supply circuit good layout practice is recommended. Mount components as close together as possible to minimize stray inductance and capacitance. Also use a large ground plane to minimize noise leakage into other circuitry.
C1A
"1"
SHDN
5
VOUT
TC1240 DEMO CARD
VOUT = 2 x VIN
Figure 5. Paralleling Multiple Devices to Reduce Output Resistance
PARALLELING DEVICES
To reduce the value of ROUT, multiple TC1240s can be connected in parallel (Figure 5). The output resistance will be reduced by a factor of N where N is the number of TC1240s. Each device will require its own pump capacitor (C1x), but all devices may share one resevoir capacitor (C2).
The TC1240 Demo Card is a 1.25" x 1.0" card containing a TC1240 and all of the necessary external components that allow the user to evaluate the device's ability to generate a 2X non-regulated output voltage. The demo card is fully assembled with the required external capacitors along with a variable load resistor that allows the user to vary the output load current of the output stage. For convenience, several test points and jumpers are available for measuring various voltages and currents on the circuit board.
Figure 6. TC1240 Demo Card Schematic
TC1240-1 7/7/00
5
Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
Figure 7. TC1240 Demo Card Assembly Drawing and Artwork
Figure 6 is a schematic of the TC1240 Demo Card, and Figure 7 shows the assembly drawing and artwork for the board. Table 3 lists the voltages that are monitored by the test points and Table 4 lists the currents that can be measured using the jumpers or the specific jumper function.
Table 3. TC1240 Demo Card Test Points TEST POINT TP1 TP2 TP3 TP4 TP5 TP6 TP7 VOLTAGE MEASUREMENT DEMO CARD POWER SUPPLY INPUT[+2.5V to +4.0V] GROUND GROUND TC1240 OUTPUT (2 x VIN) TC1240 SHDN INPUT TC1240 VIN SUPPLY VOLTAGE EXTERNAL SHDN INPUT
Table 4. TC1240 Demo Card Jumpers JUMPER J1 J2 J3 J4 CURRENT MEASUREMENT / JUMPER FUNCTION TC1240 QUIESCENT CURRENT TC1240 LOAD CURRENT TC1240 SHDN INPUT CURRENT CONNECT EXTERNAL SHDN INPUT TO VIN (i.e. SHDN ENABLE)
TC1240-1 7/7/00
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Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
TYPICAL CHARACTERISTICS
700 600 500 400 300 200 100 0
2.00
Supply Current vs. Supply Voltage (No Load)
3.00
4.00
5.00
6.00
Supply Voltage (V)
450 400 350 300 250 200 150 100 50 0 -50
Supply Current vs. Temperature (No Load)
VIN = 4.0V
VIN = 2.8V
-25
0
25 50 75 Temperature (C)
100
125
Output Source Resistance vs. Supply Voltage (with Rload = 1K) 20 15
15 25 20
Output Source Resistance vs. Temperature (with Rload = 1K)
VIN = 2.8V VIN = 4.0V
10
10
5
5
0 2.00
3.00
4.00 Supply Voltage (V)
5.00
6.00
0 -50
-25
0
25 50 75 Temperature (C)
100
125
Output Voltage Drop Vs Load Current 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 5 10 15 20
100% 90% 80%
Power Efficiency Vs Load Current
VIN = 4.0V VIN = 2.5V VIN = 3.5V
VIN = 2.8V VIN = 4.0V
70% 60% 50% 40% 30% 20% 10%
\
25
30
35
40
45
50
0% 0 5 10 15 20 25 30 35 40 45 50 Load Current (mA)
Load Current (mA)
TC1240-1 7/7/00
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Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
TYPICAL CHARACTERISTICS (Cont.)
SWITCHING FREQUENCY (KHz)
MARKING 6-Pin SOT-23A
Switching Frequency vs. Temperature 100 80 60 40 20 0 -50
V IN = 4.0V V IN = 2.8V
3
&
-25 0 25 50 75 100 125
represent part number code + temperature range (two-digit code) Code DN
D N
TC1240 1240ECH Ex: 1240ECH =
TEMPERATURE (C)
represents year and 2-month code represents lot ID number
TAPING FORM
Component Taping Orientation for 6-Pin SOT-23A (EIAJ SC-74) Devices
PIN 1
User Direction of Feed
Device Marking Device Marking
User Direction of Feed
W
PIN 1 Standard Reel Component Orientation For TR Suffix Device (Mark Right Side Up)
P Reverse Reel Component Orientation For RT Suffix Device (Mark Upside Down)
Carrier Tape, Number of Components Per Reel and Reel Size
Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size
6-Pin SOT-23A
8 mm
4 mm
3000
7 in
TC1240-1 7/7/00
8
Positive Doubling Charge Pump with Shutdown in SOT Package TC1240
PACKAGE DIMENSIONS
6-Pin SOT-23A (EIAJ SC-74)
.075 (1.90) REF.
.122 (3.10) .098 (2.50) .020 (0.50) .014 (0.35)
.069 (1.75) .059 (1.50)
.037 (0.95) REF. .118 (3.00) .110 (2.80)
.057 (1.45) .035 (0.90) .006 (0.15) .000 (0.00)
10 MAX. .024 (0.60) .004 (0.10)
.008 (0.20) .004 (0.09)
Dimensions: inches (mm)
Sales Offices
TelCom Semiconductor, Inc. 1300 Terra Bella Avenue P.O. Box 7267 Mountain View, CA 94039-7267 TEL: 650-968-9241 FAX: 650-967-1590 E-Mail: liter@telcom-semi.com
TC1240-1 7/7/00
TelCom Semiconductor, GmbH Lochhamer Strasse 13 D-82152 Martinsried Germany TEL: (011) 49 89 895 6500 FAX: (011) 49 89 895 6502 2 9
TelCom Semiconductor H.K. Ltd. 10 Sam Chuk Street, Ground Floor San Po Kong, Kowloon Hong Kong TEL: (011) 852-2350-7380 FAX: (011) 852-2354-9957

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