M
Features
TC1121
Package Type
8-Pin PDIP
FC
CAP
+
1
2
8 V+
100mA Charge Pump Voltage Converter with Shutdown
• Optional High-Frequency Operation Allows Use of
Small Capacitors
• Low Operating Current (FC = GND)
- 50µA
• High Output Current (100mA)
• 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
- 10kHz to 200kHz
• Power-Saving Shutdown Input
• Available in 8-Pin MSOP, 8-Pin PDIP and 8-Pin
Small Outline (SOIC) Packages
TC1121CPA
7 OSC
GND 3
TC1121EPA
6 SHDN
4
5 V
OUT
CAP
–
8-Pin SOIC
8-Pin MSOP
FC
CAP
+
GND
CAP
–
1
8 V+
Applications
•
•
•
•
•
Laptop Computers
Medical Instruments
Disk Drives
µP-Based
Controllers
Process Instrumentation
2
TC1121EOA
7 OSC
3
TC1121CUA
6 SHDN
TC1121COA
TC1121EUA
4
5 V
OUT
General Description
The TC1121 is a charge pump converter with 100mA
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 10kHz (at V
+
= 5V) when the frequency control input
(FC) is connected to ground. The oscillator frequency
increases to 200kHz when FC is connected to V
+
,
allowing the use of smaller capacitors. Operation at
sub-10kHz frequencies results in lower quiescent
NScurrent 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
NSconnected OSC. Typical supply current at 10kHz is
50µA, and falls to less than 1µA 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.
Device Selection Table
Part
Number
TC1121COA
TC1121CPA
TC1121CUA
TC1121EOA
TC1121EPA
TC1121EUA
Package
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
2002 Microchip Technology Inc.
DS21358B-page 1
TC1121
Functional Block Diagram
1
AP
AP
HDN
SC
Control
C1121
UT
C
RC
Oscillator
witch
atrix
2
SC
ogic
ircuits
ND
DS21358B-page 2
2002 Microchip Technology Inc.
TC1121
1.0
ELECTRICAL
CHARACTERISTICS
*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
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
Absolute Maximum Ratings*
Supply Voltage (V
DD
) ............................................... 6V
OSC, FC, SHDN Input Voltage .....-0.3V to (V
+
+ 0.3V)
Output Short Circuit Duration ........................... 10 Sec.
Package Power Dissipation (T
A
≤
70°C)
8-Pin PDIP ............................................... 730mW
8-Pin SOIC ............................................... 470mW
8-Pin MSOP ............................................. 333mW
Operating Temperature Range
C Suffix............................................ 0°C to +70°C
E Suffix......................................... -40°C to +85°C
Storage Temperature Range.............. -65°C to +150°C
TC1121 ELECTRICAL SPECIFICATIONS
Electrical Characteristics:
T
A
= 0°C to 70°C (C suffix), -40°C to +85°C (E suffix), V
+
= 5V ±10% C
OSC
= Open, C1, C2 = 10
µ
F,
FC = V
+
, SHDN = V
IH
, typical values are at T
A
= 25°C unless otherwise noted.
Symbol
I
DD
I
SHUTDOWN
V
+
V
IH
V
IL
I
IN
R
OUT
I
OUT
F
OSC
P
EFF
Parameter
Active Supply Current
Shutdown Supply Current
Supply Voltage
SHDN Input Logic High
SHDN Input Logic Low
Input Leakage Current
Output Source Resistance
Output Current
Oscillator Frequency
Power Efficiency
Min
—
—
—
2.4
V
DD
x 0.8
—
-1
-4
—
60
5
100
—
93
94
—
99
Typ
50
0.6
0.2
—
—
—
—
—
12
100
10
200
—
97
97
92
99.9
—
—
—
—
—
—
kHz
%
Max
100
1
1.0
5.5
—
0.4
1
4
20
Units
µ
A
mA
µ
A
Test Conditions
R
L
= Open, FC = Open or GND
R
L
= Open, FC = V
+
SHDN = 0V
V
V
V
µ
A
Ω
SHDN, OSC
FC pin
I
OUT
= 60mA
V
OUT
= more negative than -3.75V
Pin 7 Open, Pin 1 Open or GND
SHDN = V
IH
, Pin 1 = V
+
FC = GND for all
R
L
= 2k between V
+
and V
OUT
R
L
= 1k
Ω
between V
OUT
and GND
I
L
= 60mA to GND
R
L
= Open
V
EFF
Note
1:
Voltage Conversion Efficiency
%
Connecting any input terminal to voltages greater than V
+
or less than GND may cause destructive latch-up. It is recommended that no
inputs from sources operating from external supplies be applied prior to "power up" of the TC1121.
2002 Microchip Technology Inc.
DS21358B-page 3
TC1121
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
Pin No.
(8-Pin MSOP,
PDIP, SOIC)
1
2
3
4
5
6
7
8
PIN FUNCTION TABLE
Symbol
FC
CAP
+
GND
CAP
–
Description
Frequency control for internal oscillator, FC = open, F
OSC
= 10kHz typ; FC = V
+
, F
OSC
= 200kHz
typ; FC has no effect when OSC pin is driven externally.
Charge-pump capacitor, positive terminal.
Power-supply ground input.
Charge-pump capacitor, negative terminal.
Output, negative voltage.
Shutdown.
Oscillator control input. An external capacitor can be added to slow the oscillator. Take care to
minimize stray capacitance. An external oscillator also may be connected to overdrive OSC.
Power-supply positive voltage input.
OUT
SHDN
OSC
V
+
DS21358B-page 4
2002 Microchip Technology Inc.
TC1121
3.0
3.1
APPLICATIONS
Negative Voltage Converter
3.2
Changing Oscillator Frequency
The TC1121’s clock frequency is controlled by four
modes:
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).
TABLE 3-1:
FC
Open
FC = V
+
Open or
FC = V
+
Open
Open
Open
OSCILLATOR FREQUENCY
MODES
OSC
Oscillator Frequency
10kHz
200kHz
See Typical Operating
Characteristics
External Clock Frequency
FIGURE 3-1:
CHARGE PUMP
INVERTER
.4V to 5.5V
C
AP
N
External Capacitor
External Clock
SC
C1121
1
ND
AP
HDN
UT
SHDN*
UT
The oscillator runs at 10kHz (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 100mV 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 5kHz 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.
2
SHDN should be tied to V
N
if not used.
The TC1121 is not sensitive to load current changes,
although its output is not actively regulated. A typical
output source resistance of 11.8Ω means that an input
of +5V results in -5V output voltage under light load,
and only decreases to -3.8V typ with a 100mA 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:
V
RIPPLE
= I
OUT
/2(f
PUMP
) (C2) + I
OUT
(ESR
C2
)
Where f
PUMP
is 5kHz (one half the nominal 10kHz
oscillator frequency), and C2 = 150µF with an ESR of
0.2Ω, ripple is about 90mV with a 100mA load current.
If C2 is raised to 390µF, the ripple drops to 45mV.
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.
2002 Microchip Technology Inc.
DS21358B-page 5
京公网安备 11010802033920号
EEWORLD
