TC962EPA Microchip Technology, TC962EPA Datasheet - Page 5

• Manufacturer Part Number: TC962EPA
• Description: IC CHARGE PUMP DC/DC CONV 8-DIP
• Manufacturer: Microchip Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of TC962EPA

• 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: 80mA
• Frequency - Switching: 12kHz ~ 24kHz
• 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: 80 mA (Max)
• 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

3.0
3.1
The TC962 is a capacitive pump (sometimes called a
switched capacitor circuit), where four MOSFET
switches control the charge and discharge of a
capacitor.
The functional block diagram shows how the switching
action works. SW1 and SW2 are turned on simulta-
neously, charging C
assumes that the on resistance of the MOSFETs in
series with the capacitor results in a charging time
(3 time constants) that is less than the on time provided
by the oscillator frequency as shown:
In the next cycle, SW1 and SW2 are turned off and after
a very short interval of all switches being off (this
prevents large currents from occurring due to cross
conduction), SW3 and SW4 are turned on. The charge
in C
inverted. In this way, a negative voltage is now derived.
An oscillator supplies pulses to a flip-flop that is then
fed to a set of level shifters. These level shifters then
drive each set of switches at one-half the oscillator
frequency.
The oscillator has two pins that control the frequency of
oscillation. Pin 7 can have a capacitor added that is
returned to ground. This will lower the frequency of the
oscillator by adding capacitance to the timing capacitor
internal to the TC962. Grounding pin 6 will turn on a
FIGURE 3-2:
© 2006 Microchip Technology Inc.
P
3 (R
is then transferred to C
DS(ON)
APPLICATIONS INFORMATION
Theory of Operation
C
P1
+
10 μF
C
Combined Negative Converter and Positive Multiplier
Lowering Output Resistance by Paralleling Devices
C
P
P2
) < C
1
2
3
4
P
+
TC962
10 μF
to the supply voltage, V
Typical Applications
P
/(0.5 f
2
3
4
1
C
P1
TC962
+
8
7
6
5
V +
OSC
R
, but with the polarity
C
P2
)
8
7
6
5
+
+
V +
V
10 μF
OUT
10 μF
= –V +
2
3
4
1
TC962
IN
V
D1
. This
V
C
D2
R1
8
7
6
5
+
C
R
10 μF
V
+
2V –2V
OUT
+
10 μF
=
V
D
OUT
current source and double the frequency. This will
double the charge current going into the internal
capacitor, as well as any capacitor added to pin 7.
A Zener diode has been added to the TC962 for use as
a reference in building external regulators. This Zener
runs from pin 1 to ground.
3.2
All CMOS structures contain a parasitic SCR. Care
must be taken to prevent any input from going above or
below the supply rail, or latch-up will occur. The result
of latch-up is an effective short between V
Unless the power supply input has a current limit, this
latch-up phenomena will result in damage to the
device. (See AN763, Latch-up Protection for MOSFET
Drivers.)
FIGURE 3-1:
NC
C
P
+
10 μF
C
2
3
4
P
1
Latch-Up
+
TC962
10 μF
Positive Voltage Multiplier
1
2
3
4
1
2
3
4
TC962
TC962
8
7
6
5
690
Split V + In Half
V +
Test Circuit
C
P
C
+
8
7
6
5
8
7
5
R
10 μF
V +
V
+
D1
V
10 μF
C
D2
P
+
V
C
OUT
OSC
10 μF
C
DS21484C-page 5
TC962
V
2V –2V
R
= V
OUT
+
+
2
+
DD
=
D
10 μF
R
I
I
S
L
and V
L
V
(+5V)
V
(–5V)
+
OUT
SS
.