TC1121EPA Microchip Technology, TC1121EPA Datasheet - Page 5

• Manufacturer Part Number: TC1121EPA
• Description: IC CHARGE PUMP CONV 100MA 8-DIP
• Manufacturer: Microchip Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of TC1121EPA

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -2.4 ~ -5.5 V
• Current - Output: 100mA
• Frequency - Switching: 10kHz ~ 200kHz
• Voltage - Input: 2.4 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Power - Output: 730mW
• Primary Input Voltage: 5V
• No. Of Outputs: 1
• Output Voltage: -5.5V
• Output Current: 100mA
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Power Dissipation Pd: 470mW
• Function: Inverting
• Maximum Operating Temperature: 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 158-1063; 158-1063

3.0
3.1
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).
FIGURE 3-1:
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 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:
V
Where f
oscillator frequency), and C2 = 150 μF with an ESR of
0.2Ω, ripple is about 90 mV with a 100 mA load current.
If C2 is raised to 390 μF, the ripple drops to 45 mV.
© 2006 Microchip Technology Inc.
RIPPLE
C1
*SHDN should be tied to V
+
–
PUMP
= I
APPLICATIONS
Negative Voltage Converter
OUT
1
2
3
4
is 5 kHz (one half the nominal 10 kHz
/2(f
FC
CAP
GND
CAP
TC1121
PUMP
+
–
Charge Pump Inverter
) (C2) + I
SHDN
V
OSC
IN
OUT
V
if not used.
IN
2.4V to 5.5V
8
7
6
5
OUT
(ESR
–
+
SHDN*
C2
C2
)
V
OUT
3.2
The TC1121’s clock frequency is controlled by four
modes:
TABLE 3-1:
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
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
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
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.
Open
FC = V
Open or
FC = V
Open
+
and GND may overdrive OSC in the Inverter mode.
FC
+
and CAP
+
+
Changing Oscillator Frequency
Capacitor Selection
Open
Open
External Capacitor See Typical Operating
External Clock
–
is half that of the oscillator. In addition,
OSC
OSCILLATOR FREQUENCY
MODES
10 kHz
200 kHz
Characteristics
External Clock Frequency
Oscillator Frequency
TC1121
DS21358C-page 5