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TCM680COA

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18
TCM680
DS21486C-page 4 © 2005 Microchip Technology Inc.
2.0 TYPICAL PERFORMANCE CURVES
Note: Unless otherwise indicated, V
IN
= +5V, T
A
= +25°C.
FIGURE 2-1: Output Resistance vs. V
IN
.
FIGURE 2-2: Supply Current vs. V
IN
.
FIGURE 2-3: Output Source Resistance
vs. Temperature.
FIGURE 2-4: V
OUT
+
or V
OUT
-
vs. Load
Current.
FIGURE 2-5: Output Voltage vs. Output
Current.
Note: The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
1
2
3
456
V
IN
(V)
R
OUT
300
250
200
150
100
Output Resistance (Ω)
C
1
= C
4
= 10 μF
1
2
3
456
V
IN
(V)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Supply Current (mA)
R
L
= ∞
R
OUT
-50
0
50 100
Tem
p
erature
(
˚C
)
180
160
140
120
100
Output Source Resistance (Ω)
I
OUT
= 10 mA
0
5
10
1
5
Load Current (mA)
10.0
9.0
8.0
7.0
V
OUT
(V)
10.0
9.0
8.0
7.0
V
OUT
(V)
0
2
4
6810
Output Current (mA) From V
OUT
+
To V
OUT
–
© 2005 Microchip Technology Inc. DS21486C-page 5
TCM680
3.0 PIN DESCRIPTION
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 First Charge Pump Capacitor (C
1
-
)
Negative connection for the charge pump capacitor
(flying capacitor) used to transfer charge from the input
source to a second charge pump capacitor. This
charge pump capacitor is used to double the input volt-
age and store the charge in the second charge pump
capacitor.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output resistance.
3.2 Second Charge Pump Capacitor
(C
2
+
)
Positive connection for the second charge pump
capacitor (flying capacitor) used to transfer charge from
the first charge pump capacitor to the output.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output resistance.
3.3 Second Charge Pump Capacitor
(C
2
-
)
Negative connection for the second charge pump
capacitor (flying capacitor) used to transfer charge from
the first charge pump capacitor to the output. Proper
orientation is imperative when using a polarized
capacitor.
3.4 Negative Output Voltage (V
OUT
-
)
Negative connection for the negative charge pump out-
put capacitor. The negative charge pump output capac-
itor supplies the output load during the first, third and
fourth phases of the switching cycle. During the second
phase of the switching cycle, charge is restored to the
negative charge pump output capacitor. The negative
output voltage magnitude is approximately twice the
input voltage.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output ripple.
3.5 Ground (GND)
Input zero volt reference.
3.6 Power Supply Input (V
IN
)
Positive power supply input voltage connection. It is
recommended that a low ESR (equivalent series resis-
tance) capacitor be used to bypass the power supply
input to ground (GND).
3.7 First Charge Pump Capacitor (C
1
+
)
Positive connection for the charge pump capacitor (fly-
ing capacitor) used to transfer charge from the input
source to a second charge pump capacitor. Proper
orientation is imperative when using a polarized
capacitor.
3.8 Positive Output Voltage (V
OUT
+
)
Positive connection for the positive charge pump out-
put capacitor. The positive charge pump output capac-
itor supplies the output load during the first, second and
third phases of the switching cycle. During the fourth
phase of the switching cycle, charge is restored to the
positive charge pump output capacitor. The positive
output voltage magnitude is approximately twice the
input voltage.
It is recommended that a low ESR (equivalent series
resistance) capacitor be used. Additionally, larger
values will lower the output ripple.
Pin No.
(8-Pin PDIP,
SOIC)
Symbol Description
1C
1
-
Input. First charge pump
capacitor. Negative
connection
2C
2
+
Input. Second charge pump
capacitor. Positive
connection.
3C
2
-
Input. Second charge pump
capacitor. Negative
connection.
4V
OUT
-
Output. Negative Output
voltage
5 GND Input. Ground connection.
6V
IN
Input. Power supply.
7C
1
+
Input. First charge pump
capacitor. Positive
connection.
8V
OUT
+
Output. Positive Output
Voltage.
TCM680
DS21486C-page 6 © 2005 Microchip Technology Inc.
4.0 DETAILED DESCRIPTION
4.1 V
OUT
-
Charge Storage - Phase 1
The positive side of capacitors C
1
and C
2
are con-
nected to +5V at the start of this phase. C
1
+
is then
switched to ground and the charge in C
1
–
is transferred
to C
2
–
. Since C
2
+
is connected to +5V, the voltage
potential across capacitor C
2
is now 10V.
FIGURE 4-1: Charge Pump - Phase 1.
4.2 V
OUT
-
Transfer - Phase 2
Phase two of the clock connects the negative terminal
of C
2
to the V
OUT
-
storage capacitor C
3
and the positive
terminal of C
2
to ground, transferring the generated
-10V to C
3
. Simultaneously, the positive side of capac-
itor C
1
is switched to +5V and the negative side is
connected to ground.
FIGURE 4-2: Charge Pump - Phase 2.
4.3 V
OUT
+
Charge Storage - Phase 3
The third phase of the clock is identical to the first
phase – the charge stored in C
1
produces -5V in the
negative terminal of C
1
, which is applied to the negative
side of capacitor C
2
. Since C
2
+
is at +5V, the voltage
potential across C
2
is 10V.
FIGURE 4-3: Charge Pump - Phase 3.
4.4 V
OUT
+
Transfer - Phase 4
The fourth phase of the clock connects the negative
terminal of C
2
to ground and transfers the generated
10V across C
2
to C
4
, the V
OUT
+
storage capacitor.
Simultaneously, the positive side of capacitor C
1
is
switched to +5V and the negative side is connected to
ground, and the cycle begins again.
FIGURE 4-4: Charge Pump - Phase 4.
V
OUT
-
V
OUT
+
-5V
SW
4
SW
1
SW
2
SW
3
C
4
+
–
+
+
–
–
+
–
V
IN
= +5V
C
2
C
3
C
1
V
OUT
-
V
OUT
+
-5V
SW
4
SW
1
SW
2
SW
3
C
4
+
–
+
+
–
–
+
–
+5V
C
2
C
3
C
1
-10V
V
OUT
-
V
OUT
+
-5V
SW
4
SW
1
SW
2
SW
3
C
4
+
–
+
+
–
–
+
–
V
IN
= +5V
C
2
C
3
C
1
-10V
V
OUT
-
V
OUT
+
-5V
SW
4
SW
1
SW
2
SW
3
C
4
+
–
+
+
–
–
+
–
+5V
C
2
C
3
C
1
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18

TCM680COA

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