TC7662AEPA Microchip Technology, TC7662AEPA Datasheet - Page 6

• Manufacturer Part Number: TC7662AEPA
• Description: IC CHARGE PUMP DC/DC CONV 8-DIP
• Manufacturer: Microchip Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of TC7662AEPA

• Package / Case: 8-DIP (0.300", 7.62mm)
• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -3 ~ -18 V
• Current - Output: 40mA
• Frequency - Switching: 12kHz
• Voltage - Input: 3 ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Power - Output: 730mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: Through Hole
• Function: Inverting
• Output Voltage: - 18 V to - 3 V
• Output Current: 40 mA
• Maximum Operating Temperature: + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

TC7662A
4.0
4.1
The majority of applications will undoubtedly utilize the
TC7662A for generation of negative supply voltages.
Figure 4-1 shows typical connections to provide a
negative supply where a positive supply of +3V to +18V
is available.
FIGURE 4-1:
The output characteristics of the circuit in Figure 4-1
are those of a nearly ideal voltage source in series with
a resistance as shown in Figure 4-1b. The voltage
source has a value of -(V
(R
MOS switches (shown in the Functional Block
Diagram), the switching frequency, the value of C
C
and C
DS21468B-page 6
10µF
R
O
, and the ESR (equivalent series resistance) of C
) is a function of the ON resistance of the internal
(f
R
PUMP
O
R
+
. A good first order approximation for R
≅ 2(R
TYPICAL APPLICATIONS
Simple Negative Voltage
Converter
=
1
2
3
4
SW1
f
ESR
OSC
2
TC7662A
+ R
A
, R
CP
SW2
SWX
) +
SIMPLE NEGATIVE
CONVERTER AND ITS
OUTPUT EQUIVALENT
10µF
f
PUMP
8
7
6
5
+ ESR
= MOSFET switch resistance)
V
DD
–
+
DD
1
x C
). The output impedance
CP
V
) + 2(R
P
OUT
+ ESR
= -V+
SW3
CR
V
V
V
V
+ R
DD
DD
DD
DD
–
+
R
O
SW4
O
B
is:
P
V
+
OUT
and
P
Combining the four R
R
voltage and temperature (See Section 5.0, Typical
Characteristics “Output Source Resistance” graphs),
typically 23Ω at +25°C and 5V. Careful selection of C
and C
output impedance.
reduce the 1/(f
capacitors will lower the ESR term. Increasing the
oscillator frequency will reduce the 1/(f
but may have the side effect of a net increase in output
impedance when C
time to fully charge the capacitors every cycle. In a typ-
ical application when f
10µF:
Since the ESRs of the capacitors are reflected in the
output impedance multiplied by a factor of 5, a high
value could potentially swamp out a low 1/(f
term, rendering an increase in switching frequency
or filter capacitance ineffective. Typical electrolytic
capacitors may have ESRs as high as 10Ω.
SW
R
O
R
, the total switch resistance, is a function of supply
≅ 2 x 23 +
O
R
≅ 2 x R
will reduce the remaining terms, minimizing the
R
SW
(5 x 12
O
PUMP
+
≅ (46 + 20 + 5 x ESR
f
PUMP
P
3
SWX
> 10µF and there is not enough
x C
OSC
x 10 x 10
High
1
1
 2002 Microchip Technology Inc.
x C
P
terms as R
= 12kHz and C = C
) component, and low ESR
P
+ 4 x ESR
value
-6
)
+ 4 x ESR
C
) Ω
SW
PUMP
CP
capacitors
, we see that:
+ ESR
CP
PUMP
x C
+ ESR
P
CR
P
= C
) term,
x C
Ω
CR
R
will
P
=
P
)