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PDF TC1121 Data sheet ( Hoja de datos )
| Número de pieza | TC1121 | |
| Descripción | 100mA Charge Pump Voltage Converter with Shutdown | |
| Fabricantes | Microchip | |
| Logotipo |  |
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Obsolete Device
TC1121
100mA Charge Pump Voltage Converter with Shutdown
Features:
• Optional High-Frequency Operation Allows Use of
Small Capacitors
• Low Operating Current (FC = Open):
- 50 A
• High Output Current (100 mA)
• Converts a 2.4V to 5.5V Input Voltage to a
Corresponding Negative Output Voltage
(Inverter mode)
• Uses Only 2 Capacitors; No Inductors Required
• Selectable Oscillator Frequency:
- 10 kHz to 200 kHz
• Power-Saving Shutdown Input
• Available in 8-Pin MSOP, 8-Pin PDIP and 8-Pin
Small Outline (SOIC) Packages
Applications:
• Laptop Computers
• Medical Instruments
• Disk Drives
• P-Based Controllers
• Process Instrumentation
Device Selection Table
Part
Number
Package
TC1121COA
TC1121CPA
TC1121CUA
TC1121EOA
TC1121EPA
TC1121EUA
8-Pin SOIC
8-Pin PDIP
8-Pin MSOP
8-Pin SOIC
8-Pin PDIP
8-Pin MSOP
Operating
Temp.
Range
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
Package Type
8-Pin PDIP
FC 1
8 V+
CAP+ 2 TC1121CPA 7 OSC
GND 3 TC1121EPA 6 SHDN
CAP– 4
5 VOUT
8-Pin SOIC
8-Pin MSOP
FC 1
8 V+
TC1121COA
CAP+ 2 TC1121EOA 7 OSC
GND 3 TC1121CUA 6 SHDN
TC1121EUA
CAP– 4
5 VOUT
General Description:
The TC1121 is a charge pump converter with 100 mA
output current capability. It converts a 2.4V to 5.5V
input to a corresponding negative output voltage. As
with all charge pump converters, the TC1121 uses no
inductors saving cost, size and EMI.
An on-board oscillator operates at a typical frequency
of 10 kHz (at V+ = 5V) when the frequency control input
(FC) is left open. The oscillator frequency increases to
200 kHz when FC is connected to V+, allowing the use
of smaller capacitors. Operation at sub-10 kHz
frequencies results in lower quiescent current and is
accomplished with the addition of an external capacitor
from OSC (pin 7) to ground. The TC1121 also can be
driven from an external clock connected OSC. Typical
supply current at 10 kHz is 50 A, and falls to less than
1 A when the shutdown input is brought low, whether
the internal or an external clock is used. The TC1121 is
available in 8-pin SOIC, MSOP and PDIP packages.
2006-2014 Microchip Technology Inc.
DS20001358D-page 1
1 page  
3.0 APPLICATIONS
3.1 Negative Voltage Converter
The TC1121 is typically used as a charge-pump voltage
inverter. C1 and C2 are the only two external capacitors
used in the operating circuit (Figure 3-1).
+
C1
–
2.4V to 5.5V
1
FC
2 CAP+
8
VIN
OSC 7
TC1121
36
GND SHDN
SHDN*
4 CAP–
VOUT 5
–
C2
+
VOUT
*SHDN should be tied to VIN if not used.
FIGURE 3-1:
Charge Pump Inverter
The TC1121 is not sensitive to load current changes,
although its output is not actively regulated. A typical
output source resistance of 11.8 means that an input
of +5V results in -5V output voltage under light load,
and only decreases to -3.8V typ with a 100 mA load.
The supplied output current is from capacitor C2 during
one-half the charge-pump cycle. This results in a
peak-to-peak ripple of:
VRIPPLE = IOUT/2(fPUMP) (C2) + IOUT (ESRC2)
Where fPUMP is 5 kHz (one half the nominal 10 kHz
oscillator frequency), and C2 = 150 F with an ESR of
0.2, ripple is about 90 mV with a 100 mA load current.
If C2 is raised to 390 F, the ripple drops to 45 mV.
TC1121
3.2 Changing Oscillator Frequency
The TC1121’s clock frequency is controlled by four
modes:
TABLE 3-1: OSCILLATOR FREQUENCY
MODES
FC
OSC
Oscillator Frequency
Open
FC = V+
Open or
FC = V+
Open
Open
10 kHz
Open
200 kHz
External Capacitor See Typical Operating
Characteristics
External Clock
External Clock Frequency
The oscillator runs at 10 kHz (typical) when FC and
OSC are not connected. The oscillator frequency is
lowered by connecting a capacitor between OSC and
GND, but FC can still multiply the frequency by 20
times in this mode.
An external clock source that swings within 100 mV of
V+ and GND may overdrive OSC in the Inverter mode.
OSC can be driven by any CMOS logic output. When
OSC is overdriven, FC has no effect.
Note that the frequency of the signal appearing at
CAP+ and CAP– is half that of the oscillator. In addition,
by lowering the oscillator frequency, the effective
output resistance of the charge-pump increases. To
compensate for this, the value of the charge-pump
capacitors may be increased.
Because the 5 kHz output ripple frequency may be low
enough to interfere with other circuitry, the oscillator
frequency can be increased with the use of the FC pin
or an external oscillator. The output ripple frequency is
half the selected oscillator frequency. Although the
TC1121’s quiescent current will increase if the clock
frequency is increased, it allows smaller capacitance
values to be used for C1 and C2.
3.3 Capacitor Selection
In addition to load current, the following factors affect
the TC1121 output voltage drop from its ideal value 1)
output resistance, 2) pump (C1) and reservoir (C2)
capacitor ESRs and 3) C1 and C2 capacitance.
The voltage drop is the load current times the output
resistance. The loss in C2 is the load current times C2’s
ESR; C1’s loss is larger because it handles currents
greater than the load current during charge-pump
operation. Therefore, the voltage drop due to C1 is
about four times C1’s ESR multiplied by the load
current, and a low (or high) ESR capacitor has a
greater impact on performance for C1 than for C2.
In general, as the TC1121’s pump frequency increases,
capacitance values needed to maintain comparable
ripple and output resistance diminish proportionately.
2006-2014 Microchip Technology Inc.
DS20001358D-page 5
5 Page 
TC1121
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Technical support is available through the web site
at: http://microchip.com/support
2006-2014 Microchip Technology Inc.
DS20001358D-page 11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet TC1121.PDF ] | |
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