View TC828AECT_1322850.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

TC828A Switched Capacitor Voltage Converter
FEATURES
s s s s s s s s Charge Pump in 5-Pin SOT-23A Package >95% Voltage Conversion Efficiency Voltage Inversion and/or Doubling Low 38A Quiescent Current Operates from +1.8V to +5.5V Up to 25mA Output Current Only Two External Capacitors Required Lower Power Version of TCM828
GENERAL DESCRIPTION
The TC828A is a CMOS "charge-pump" voltage converter in an ultra-small 5-Pin SOT-23A package. It can invert and/or double an input voltage that can range from +1.8V to +5.5V. Conversion efficiency is typically >95%, and switching frequency is 12KHz. The external component requirement is only two capacitors (10F nominal) for standard voltage inverter applications. With a few additional components a positive doubler can also be built. All other circuitry, including control, oscillator, power MOSFETs are integrated on-chip. Supply current is 38A typically. The TC828A is available in a 5-Pin SOT-23A surface mount package.
APPLICATIONS
s s s s s LCD Panel Bias Cellular Phones Pagers PDAs, Portable Dataloggers Battery-Powered Devices
ORDERING INFORMATION
Part No.
TC828AECT
PIN CONFIGURATION 5-Pin SOT-23A
Package
5-Pin SOT-23A
Temp. Range
- 40C to +85C
NOTE: 5-Pin SOT-23A is equivalent to EIAJ-SC74A.
OUT
1
5
C+
VIN
2
TC828ECT
C-
3
4
GND
NOTE: *5-Pin SOT-23A is equivalent to EIAJ SC-74A
TYPICAL OPERATING CIRCUIT Voltage Inverter
C+ C1 C- TC828A VIN INPUT
OUT GND C2
V- OUTPUT
TC828A-1
5/1/00 TelCom Semiconductor reserves the right to make changes in the circuitry and specifications of its devices.
Switched Capacitor Voltage Converters TC828A
ABSOLUTE MAXIMUM RATINGS*
Input Voltage (VIN to GND) ......................... +6.0V, - 0.3V Output Voltage (OUT to GND) .................... -6.0V, + 0.3V Current at OUT Pin .................................................. 50mA Short-Circuit Duration - OUT to GND ................ Indefinite Operating Temperature Range ............... - 40C to +85C Power Dissipation (TA 70C) 5-Pin SOT-23A ...............................................240mW Storage Temperature (Unbiased) ......... - 65C to +150C Lead Temperature (Soldering, 10 sec) ................. +300C
*This is a stress rating 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 = -40C to +85C, VIN = +5V, C1 = C2 = 10 F, unless otherwise
noted. Typical values are at TA = +25C. Symbol
IDD V+ V+ FOSC PEFF VEFF ROUT
Parameter
Supply Current Minimum Supply Voltage Maximum Supply Voltage Oscillator Frequency Power Efficiency Voltage Conversion Efficiency Output Resistance
Test Conditions
RLOAD = 1 K RLOAD = 1 K
Min
-- 1.8 -- 6 -- 95 -- --
Typ
38 -- -- 12 96 99.9 25 --
Max
80 -- 5.5 20 -- -- 50 65
Unit
A V V KHz % %
RLOAD = 1 K, TA = +25C RLOAD = IOUT = 5 mA, TA = +25C TA = -40C to +85C
NOTE: 1. Capacitor contribution is approximately 20% of the output impedance [ESR = 1 / pump frequency x capacitance)]. 2. All - 40C to +85C specifications above are guaranteed by design.
PIN DESCRIPTION
Pin No. (5-Pin SOT-23A)
1 2 3 4 5
Symbol
OUT VIN - C1 GND + C1
Description
Inverting charge pump output. Positive power supply input. Commutation capacitor negative terminal. Ground. Commutation capacitor positive terminal.
TC828A-1 5/1/00
2
Switched Capacitor Voltage Converters TC828A
DETAILED DESCRIPTION
The TC828A charge pump converter inverts the voltage applied to the VIN pin. Conversion consists of a two-phase 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. This action connects C1 across C2, restoring charge to C2. (4) Losses that occur during charge transfer (from the 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), (3) and (4) above. These losses are given by Equation 1. PLOSS (2, 3, 4) = IOUT2 x ROUT IOUT2 x
S1 IN C1 TC828 S2
[(f
1 C1
OSC)
+8RSWITCH + 4ESRC1 + ESRC2
Equation 1.
]
C2 S3 S4 VOUT = - (VIN)
The 1/(fOSC)(C1) term in Equation 1 is the effective output resistance of an ideal switched capacitor circuit (Figures 2a, 2b). The losses in the circuit due to factor (4) above are also shown in Equation 2. The output voltage ripple is given by Equation 3. PLOSS (4) = (0.5)(C1)(VIN2- VOUT2) + (0.5)(C2)(VRIPPLE2 - 2VOUTVRIPPLE)
[
] xf
OSC
Figure 1. Ideal Switched Capacitor Charge Pump
Equation 2.
APPLICATIONS INFORMATION Output Voltage Considerations
The TC828A performs voltage conversion 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 25 nominal at +25C and VIN = +5V. VOUT is approximately - 5V at light loads, and droops according to the equation below: VDROOP = IOUT x ROUT VOUT = - (VIN - VDROOP)
VRIPPLE =
IOUT +2(IOUT)(ESRC2) (fOSC)(C2)
Equation 3.
f V+ VOUT RL
C1
C2
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). (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).
TC828A-1 5/1/00
Figure 2a. Ideal Switched Capacitor Model
REQUIV V+ REQUIV = VOUT
1 f x C1
C2
RL
Figure 2b. Equivalent Output Resistance 3
Switched Capacitor Voltage Converters TC828A
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 2 RSW. Table 2 shows the output voltage ripple for various values of C2. The VRIPPLE values assume 10mA output load current and 0.1 ESRC2.
Table 1. Output Resistance vs. C1 (ESR = 0.1)
C3 10 F* VOUT 1 OUT 5 C1+ C2 10 F* RL VIN
2 3
IN
TC828 4
C1 10 F* GND
C1-
Voltage Inverter
Figure 3. Test Circuit
C1(F)
0.1 1 3.3 10 47 100
ROUT ()
850 100 42 25 18.3 17.3
Cascading Devices
Two or more TC828As can be cascaded to increase output voltage (Figure 4). If the output is lightly loaded, it will be close to (- 2 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 large negative voltage requirements see the TC682 or TCM680 data sheets.
Table 2. Output Voltage Ripple vs. C2 (ESR = 0.1) IOUT 10mA
C2(F) 1 3.3 10 47 100 VRIPPLE (mV) 835 254 85 19.7 10.3
... + VIN 2 3 3 4 5 ... C2 VOUT = -nVIN C2 2
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 depends on the configuration of the TC828A. If the device is loaded from OUT to GND it is recommended that a large value capacitor (at least equal to C1) be connected from the input to GND. If the device is loaded from IN to OUT a small (0.1 F) capacitor from IN to OUT is sufficient.
C1
4 5
TC828 "1" 1
C1
TC828 "N" 1 VOUT
Figure 4. Cascading TC828As to Increase Output Voltage
Paralleling Devices
To reduce the value of ROUT, multiple TC828As can be connected in parallel (Figure 5). The output resistance will be reduced by a factor of N where N is the number of TC828As. Each device will require it's own pump capacitor (C1), but all devices may share one reservoir capacitor (C2). However, to preserve ripple performance the value of C2 should be scaled according to the number of paralleled TC828As.
4
Voltage Inverter
The most common application for charge pump devices is the inverter (Figure 3). This application uses two external capacitors - C1 and C2 (plus a power supply bypass capacitor, if necessary). The output is equal to V- plus any IN voltage drops due to loading. Refer to Table 1 and Table 2 for capacitor selection.
TC828A-1 5/1/00
Switched Capacitor Voltage Converters TC828A
ROUT = ROUT OF SINGLE DEVICE NUMBER OF DEVICES + VIN 2 3 4 5 C1 1 ... - VOUT = VIN C2 3 4 5 ... 2
Diode Protection for Heavy Loads
When heavy loads require the OUT pin to sink large currents being delivered by a positive source, diode protection may be needed. The OUT pin should not be allowed to be pulled above ground. This is accomplished by connecting a Schottky diode (1N5817) as shown in Figure 7.
C1
TC828 "1"
TC828 "N" 1 VOUT
GND
4
TC828
Figure 5. Paralleling TC828As to Reduce Output Resistance
Voltage Doubler/Inverter
Another common application of the TC828A is shown in Figure 6. This circuit performs two functions in combination. C1 and C2 form the standard inverter circuit described above. C3 and C4 plus the two diodes form the voltage doubler circuit. C1 and C3 are the pump capacitors and C2 and C4 are the reservoir capacitors. Because both subcircuits rely on the same switches if either output is loaded, both will droop toward GND. Make sure that the total current drawn from both the outputs does not total more than 40 mA.
+ VIN D1, D2 = 1N4148
OUT
1
Figure 7. High V- Load Current
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.
3 C1 4 TC828
2
D1 1 C2 D2
- VOUT = VIN
5
C3 C4
VOUT = (2VIN) - (VFD1) - (VFD2)
Figure 6. Combined Doubler and Inverter
TC828A-1 5/1/00
5
Switched Capacitor Voltage Converters TC828A
TYPICAL CHARACTERISTICS
Circuit of Figure 3, VIN = +5V, C1 = C2 = C3, TA = +25C, unless otherwise noted.
Output Resistance vs. Supply Voltage
65 60 55 50 45 40 35 30 25 20 15 10 5 0 1.5 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V) 65 60
OUTPUT RESISTANCE () OUTPUT RESISTANCE ()
Output Resistance vs. Temperature
Output Current vs. Capacitance
45
OUTPUT CURRENT (mA)
40 35 30 25 20 15 10 5
VIN = 4.75V, VOUT = - 4.0V
55 50 45 40 35 30 25 20 15 -40 -20 0
VIN = 1.8V
VIN = 3.15V, VOUT = - 2.5V
VIN = 3.3V VIN = 5.0V
20 40 60 80
VIN = 1.9V, VOUT = -1.5V 0 5 10 15 20 25 30 35 40 45 50 CAPACITANCE (F)
0
TEMPERATURE (C)
Output Voltage Ripple vs. Capacitance
OUTPUT VOLTAGE RIPPLE (mVp-p)
Supply Current vs. Supply Voltage
45
PUMP FREQUENCY (kHz)
Pump Frequency vs. Temperature
15
500 450
SUPPLY CURRENT (A)
40
400 350 300 250 200 150 100 50 0 0 5
VIN = 4.75V, VOUT = - 4.0V VIN = 3.15V, VOUT = - 2.5V VIN = 1.9V, VOUT = - 1.5V
14 13 12 VIN = 3.3V 11 10 9 8 -40 VIN = 1.5V VIN = 5.0V
35 30 25 20 15 10 5
10
25
20
25
30
0 1.5
2
CAPACITANCE (F)
2.5 3 3.5 4 4.5 SUPPLY VOLTAGE (V)
5
5.5
-20
0
20
40
60
80
TEMPERATURE (C)
TC828A-1 5/1/00
6
Switched Capacitor Voltage Converters TC828A
TYPICAL CHARACTERISTICS (Cont.)
Circuit of Figure 3, VIN = +5V, C1 = C2 = C3, TA = +25C, unless otherwise noted.
Output Voltage vs. Output Current
0.5
OUTPUT VOLTAGE (V)
Efficiency vs. Output Current
100 90
VIN = 5.0V VIN = 2.0V VIN = 3.3V
-0.5 -1.5 -2.5 -3.5
EFFICIENCY (%)
80 VIN = 2.0V VIN = 3.3V 70 60 50 40 30 20 10
VIN = 5.0V
-4.5 -5.5 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA)
0 0 5 10 15 20 25 30 35 40 45 50 OUTPUT CURRENT (mA)
TAPING FORM
Component Taping Orientation for 5-Pin SOT-23A (EIAJ SC-74A) Devices
PIN 1
User Direction of Feed
Device Marking Device Marking
User Direction of Feed
W
PIN 1 Standard Reel Component Orientation TR Suffix Device (Mark Right Side Up)
P Reverse Reel Component Orientation 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
5-Pin SOT-23A
8 mm
4 mm
3000
7 in
TC828A-1 5/1/00
7
Switched Capacitor Voltage Converters TC828A
MARKING SOT-23A-5 represents lot ID number represents year and 2-month code
Part Numbers and Part Marking & = part number code + temperature range (two-digit code). TC828A TC828AECT
CC ex: 828ECT = kkkk
Code CC
PACKAGE DIMENSIONS
5-Pin SOT-23A (EIAJ SC-74A)
.075 (1.90) REF.
.122 (3.10) .098 (2.50) .020 (0.50) .012 (0.30) PIN 1 .122 (3.10) .106 (2.70) .057 (1.45) .035 (0.90) .006 (0.15) .000 (0.00)
.071 (1.80) .059 (1.50)
.037 (0.95) REF.
10 MAX. .024 (0.60) .004 (0.10)
.010 (0.25) .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
TC828A-1 5/1/00
TelCom Semiconductor, GmbH Lochhamer Strasse 13 D-82152 Martinsried Germany TEL: (011) 49 89 895 6500 FAX: (011) 49 89 895 6502 2 8
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

▲Up To Search▲

Price & Availability of TC828AECT

	To Download TC828AECT Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .