LM828M5 National Semiconductor, LM828M5 Datasheet - Page 7

• Manufacturer Part Number: LM828M5
• Description: IC SW CAP/INV ADJ 25MA SOT23-5
• Manufacturer: National Semiconductor
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of LM828M5

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.8 ~ -5.5 V
• Current - Output: 25mA
• Frequency - Switching: 12kHz
• Voltage - Input: 1.8 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Power - Output: 240mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LM828M5TR

Other Applications
PARALLELING DEVICES
Any number of LM828s can be paralleled to reduce the output
resistance. Each device must have its own pumping capacitor
CASCADING DEVICES
Cascading the LM828s is an easy way to produce a greater
negative voltage (e.g. A two-stage cascade circuit is shown
in Figure 4).
If n is the integer representing the number of devices cas-
caded, the unloaded output voltage V
tive output resistance is equal to the weighted sum of each
individual device:
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AVX Corp.
Sprague
Sanyo
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Manufacturer
R
out
= nR
out_1
+ n/2 R
FIGURE 4. Lowering Output Resistance by Paralleling Devices
out_2
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+ ... + R
out
is (-nV
Phone
out_n
Low ESR Capacitor Manufacturers
in
). The effec-
PL & PF series, through-hole aluminum electrolytic
TPS series, surface-mount tantalum
593D, 594D, 595D series, surface-mount tantalum
OS-CON series, through-hole aluminum electrolytic
Ceramic chip capacitors
Ceramic chip capacitors
Ceramic chip capacitors
7
C
in Figure 3. The composite output resistance is:
This can be seen by first assuming that each device is 100
percent efficient. Since the output voltage is different on each
device the output current is as well. Each cascaded device
sees less current at the output than the previous so the
R
the number of n is practically limited since the increasing of n
significantly reduces the efficiency, and increases the output
resistance and output voltage ripple.
1
OUT
, while only one output capacitor C
voltage drop is lower in each device added. Note that,
Capacitor Type
10013709
out
is needed as shown
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