LM2662M National Semiconductor, LM2662M Datasheet - Page 8

• Manufacturer Part Number: LM2662M
• Description: IC, DC/DC VOLTAGE CONVERTER, 8-SOIC
• Manufacturer: National Semiconductor

Specifications of LM2662M

• Primary Input Voltage: 5V
• No. Of Outputs: 1
• Output Current: 200mA
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +85°C
• Power Dissipation Pd: 735mW
• Supply Voltage Range: 1.5V To 5.5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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SHUTDOWN MODE
For the LM2663, a shutdown (SD) pin is available to disable
the device and reduce the quiescent current to 10 μA. Apply-
ing a voltage greater than 2V to the SD pin will bring the device
into shutdown mode. While in normal operating mode, the SD
pin is connected to ground.
CAPACITOR SELECTION
As discussed in the Simple Negative Voltage Converter sec-
tion, the output resistance and ripple voltage are dependent
on the capacitance and ESR values of the external capaci-
tors. The output voltage drop is the load current times the
output resistance, and the power efficiency is
Open
External Capacitor See Typical Performance
External Clock
(inverter mode only)
TABLE 2. LM2663 Oscillator Frequency Selection
OSC
Nichicon Corp.
AVX Corp.
Sprague
Sanyo
Murata
Taiyo Yuden
Tokin
Manufacturer
150 kHz
Characteristics
External Clock Frequency
FIGURE 3. Output Source Resistance vs Oscillator Frequency
Oscillator
(800)-831-9172
(800)-348-2496
(408)-432-8020
(708)-843-7500 PL, PF series, through-hole aluminum electrolytic
(803)-448-9411 TPS series, surface-mount tantalum
(207)-324-4140 593D, 594D, 595D series, surface-mount tantalum
(619)-661-6835 OS-CON series, through-hole aluminum electrolytic
TABLE 3. Low ESR Capacitor Manufacturers
Phone
Ceramic chip capacitors
Ceramic chip capacitors
Ceramic chip capacitors
8
Where I
and I
on-resistance, the two external capacitors and their ESRs.
Low ESR capacitors (Table 3) are recommended for both ca-
pacitors to maximize efficiency, reduce the output voltage
drop and voltage ripple. For convenience, C
ally chosen to be the same.
The output resistance varies with the oscillator frequency and
the capacitors. In Figure 3, the output resistance vs. oscillator
frequency curves are drawn for four difference capacitor val-
ues. At very low frequency range, capacitance plays the most
important role in determining the output resistance. Once the
frequency is increased to some point (such as 100 kHz for the
47 μF capacitors), the output resistance is dominated by the
ON resistance of the internal switches and the ESRs of the
external capacitors. A low value, smaller size capacitor usu-
ally has a higher ESR compared with a bigger size capacitor
of the same type. Ceramic capacitors can be chosen for their
lower ESR. As shown in Figure 3, in higher frequency range,
the output resistance using the 10 μF ceramic capacitors is
close to these using higher value tantalum capacitors.
L
2
R
Capacitor Type
Q
OUT
(V+) is the quiescent power loss of the IC device,
is the conversion loss associated with the switch
10000336
1
and C
2
are usu-