TC7662BEOA Microchip Technology, TC7662BEOA Datasheet - Page 4

• Manufacturer Part Number: TC7662BEOA
• Description: IC CHARGE PUMP DC/DC CONV 8-SOIC
• Manufacturer: Microchip Technology
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of TC7662BEOA

• Package / Case: 8-SOIC (3.9mm Width)
• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.5 ~ -15 V
• Current - Output: 20mA
• Frequency - Switching: 10kHz ~ 35kHz
• Voltage - Input: 1.5 ~ 15 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Power - Output: 470mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Function: Inverting
• Output Voltage: - 15 V to - 1.5 V
• Output Current: 20 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
• Other names: 158-1060; 158-1060

TC7662B-8 9/11/96
TC7662B
be approximated by an ideal voltage source in series with a
resistance as shown in Figure 3b. The voltage source has a
value of–(V+). The output impedance (R
the ON resistance of the internal MOS switches (shown in
Figure 2), the switching frequency, the value of C
and the ESR (equivalent series resistance) of C
good first order approximation for R
Combining the four R
4. When using polarized capacitors in the inverting mode,
5. If the voltage supply driving the TC7662B has a large
TYPICAL APPLICATIONS
Simple Negative Voltage Converter
TC7662B for generation of negative supply voltages. Figure
3 shows typical connections to provide a negative supply
where a positive supply of +1.5V to +15V is available. Keep
in mind that pin 6 (LV) is tied to the supply negative (GND)
for supply voltages below 3.5 volts.
(f
PUMP
Figure 3. Simple Negative Converter and its Output Equivalent
10 F
R
the + terminal of C
TC7662B and the – terminal of C
to GND.
source impedance (25-30 ohms), then a 2.2 F capaci-
tor from pin 8 to ground may be required to limit the
rate of rise of the input voltage to less than 2V/ sec.
R
The output characteristics of the circuit in Figure 3 can
R
The majority of applications will undoubtedly utilize the
O
+
–
O
SW
=
2 x R
, the total switch resistance, is a function of supply
2(R
1
2
3
4
ESR
f
SW1
OSC
TC7662B
SW
2
a.
+
C1
+ R
) +
, R
SW3
f
10 F
PUMP
SWX
1
8
7
6
5
SWX
must be connected to pin 2 of the
1
+ ESR
f
–
+
PUMP
terms as R
V+
x C
= MOSFET switch resistance)
1
1
x C
V OUT = –V+
C1
+ 4 x ESR
1
) + 2(R
O
2
SW
+ ESR
is:
must be connected
, we see that:
O
SW2
) is a function of
C1
C2
V+
+ ESR
+ R
–
+
R O
1
b.
and C
SW4
1
and C
C2
V OUT
+
2
. A
2
,
4
voltage and temperature (See the Output Source Resis-
tance graphs), typically 23
selection of C
minimizing the output impedance. High value capacitors will
reduce the 1/(f
tors will lower the ESR term. Increasing the oscillator fre-
quency will reduce the 1/(f
side effect of a net increase in output impedance when C
10 F and there is not enough time to fully charge the
capacitors every cycle. In a typical application when f
10kHz and C = C
R
output impedance multiplied by a factor of 5, a high value
could potentially swamp out a low 1/(f
rendering an increase in switching frequency or filter capaci-
tance ineffective. Typical electrolytic capacitors may have
ESRs as high as 10 .
Output Ripple
The total ripple is determined by 2 voltages, A and B, as
shown in Figure 4. Segment A is the voltage drop across the
ESR of C
(current flowing into C
load (current flowing out of C
current change is 2 x I
ESR
during time t
to the load. The drop at B is I
peak ripple voltage is the sum of these voltage drops:
V
O
0
– (V+)
Since the ESRs of the capacitors are reflected in the
ESR also affects the ripple voltage seen at the output.
V
C2
2 x 23 +
RIPPLE
volts. Segment B is the voltage change across C
2
at the instant it goes from being charged by C
2
, the half of the cycle when C
(
PUMP
1
R
B
(5 x 10
2 x f
O
and C
1
CHARGE PUMP DC-TO-DC
Figure 4. Output Ripple
= C
PUMP
x C
(46 + 20 + 5 x ESR
A
1
OUT
3
VOLTAGE CONVERTER
2
2
2
t
1
x 10 x 10
2
) to being discharged through the
) component, and low ESR capaci-
= 10 F:
1
will reduce the remaining terms,
x C
PUMP
, hence the total drop is 2 x I
2
OUT
© 2001 Microchip Technology Inc.
+ ESR
x C
at +25 C and 5V. Careful
2
-6
). The magnitude of this
x t
)
1
t
1
) term, but may have the
2
/C
+ 4 x ESR
C2
2
x I
C
volts. The peak-to-
PUMP
)
2
OUT
supplies current
)
x C
C1
+ ESR
1
) term,
DS21469A
OSC
OUT
1
C2
>
=
x
1
2