If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V+ to
GND, or GND to OUT)
V+ and OUT Continuous
Output Current
Output Short-Circuit
Duration to GND (Note 2)
Continuous Power
Dissipation (T
A
=
25˚C)(Note 3)
5.8V
50 mA
1 sec.
240 mW
T
JMax
(Note 3)
θ
JA
(Note 3)
Operating Junction
Temperature Range
Storage Temperature
Range
Lead Temp. (Soldering, 10
seconds)
ESD Rating (Note 7)
150˚C
300˚C/W
−40˚C to 85˚C
−65˚C to +150˚C
300˚C
2kV
Electrical Characteristics
Limits in standard typeface are for T
J
= 25˚C, and limits in
boldface
type apply over the full operating temperature range. Un-
less otherwise specified: V+ = 5V, C
1
= C
2
= 10 µF. (Note 4)
Symbol
V+
I
Q
R
OUT
f
OSC
f
SW
P
EFF
V
OEFF
Parameter
Supply Voltage
Supply Current
Output Resistance (Note 5)
Oscillator Frequency (Note 6)
Switching Frequency (Note 6)
Power Efficiency
Voltage Conversion Efficiency
Condition
R
L
=10kΩ
No Load
I
L
= 5 mA
Internal
Measured at CAP+
I
L
= 5 mA
No Load
95
12
6
Min
1.8
40
20
24
12
97
99.96
Typ
Max
5.5
75
115
65
56
28
Ω
kHz
kHz
%
%
Units
V
µA
Note 1:
Absolute maximum ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 2:
OUT may be shorted to GND for one second without damage. However, shorting OUT to V+ may damage the device and should be avoided. Also, for
temperatures above 85˚C, OUT must not be shorted to GND or V+, or the device may be damaged.
Note 3:
The maximum allowable power dissipation is calculated by using P
DMax
= (T
JMax
− T
A
)/θ
JA
, where T
JMax
is the maximum junction temperature, T
A
is the
ambient temperature, and
θ
JA
is the junction-to-ambient thermal resistance of the package.
Note 4:
In the test circuit, capacitors C
1
and C
2
are 10 µF, 0.3Ω maximum ESR capacitors. Capacitors with higher ESR will increase output resistance, reduce
output voltage and efficiency.
Note 5:
Specified output resistance includes internal switch resistance and capacitor ESR. See the details in the application information.
Note 6:
The output switches operate at one half of the oscillator frequency, f
OSC
= 2f
SW
.
Note 7:
The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
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2
LM828
Test Circuit
DS100137-3
*
C
1
and C
2
are 10 µF capacitors.
FIGURE 1. LM828 Test Circuit
Typical Performance Characteristics
Supply Current vs
Supply Voltage
(Circuit of Figure 1, V+ = 5V unless otherwise specified)
Supply Current vs
Temperature
DS100137-29
DS100137-30
Output Source Resistance
vs Supply Voltage
Output Source Resistance
vs Temperature
DS100137-31
DS100137-32
3
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LM828
Typical Performance Characteristics
specified) (Continued)
Output Voltage
vs Load Current
(Circuit of Figure 1, V+ = 5V unless otherwise
Efficiency vs
Load Current
DS100137-33
DS100137-34
Switching Frequency vs
Supply Voltage
Switching Frequency vs
Temperature
DS100137-35
DS100137-36
Connection Diagram
5-Lead Small Outline Package (M5)
DS100137-14
Actual Size
DS100137-13
Top View With Package Marking
Ordering Information
Order Number
LM828M5
LM828M5X
Package
Number
MA05B
MA05B
Package Marking
S08A (Note 8)
S08A (Note 8)
Supplied as
Tape and Reel (250 units/rail)
Tape and Reel (3000 units/rail)
Note 8:
The first letter ’S’ identifies the part as a switched capacitor converter. The next two numbers are the device number. Larger quantity reels are available upon
request.
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4
LM828
Pin Description
Pin
1
2
3
4
5
Name
OUT
V+
CAP−
GND
CAP+
Negative voltage output.
Power supply positive input.
Connect this pin to the negative terminal of the charge-pump capacitor.
Power supply ground input.
Connect this pin to the positive terminal of the charge-pump capacitor.
a function of the ON resistance of the internal MOSFET
switches, the oscillator frequency, the capacitance and the
ESR of both C
1
and C
2
. Since the switching current charging
and discharging C
1
is approximately twice as the output
current, the effect of the ESR of the pumping capacitor C
1
will be multiplied by four in the output resistance. The output
capacitor C
2
is charging and discharging at a current ap-
proximately equal to the output current, therefore, this ESR
term only counts once in the output resistance. A good
approximation of R
out
is:
Function
Circuit Description
The LM828 contains four large CMOS switches which are
switched in a sequence to invert the input supply voltage.
Energy transfer and storage are provided by external capaci-
tors.
Figure 2
illustrates the voltage conversion scheme.
When S
1
and S
3
are closed, C
1
charges to the supply
voltage V+. During this time interval, switches S
2
and S
4
are
open. In the second time interval, S
1
and S
3
are open; at the
same time, S
2
and S
4
are closed, C
1
is charging C
2
. After a
number of cycles, the voltage across C
2
will be pumped to
V+. Since the anode of C
2
is connected to ground, the output
at the cathode of C
2
equals −(V+) when there is no load
current. The output voltage drop when a load is added is
determined by the parasitic resistance (R
ds(on)
of the MOS-
FET switches and the ESR of the capacitors) and the charge
transfer loss between capacitors.
where R
SW
is the sum of the ON resistance of the internal
MOSFET switches shown in
Figure 2.
High capacitance, low ESR capacitors will reduce the output
resistance.
The peak-to-peak output voltage ripple is determined by the
oscillator frequency, the capacitance and ESR of the output
capacitor C
2
:
Again, using a low ESR capacitor will result in lower ripple.
Capacitor Selection
The output resistance and ripple voltage are dependent on
the capacitance and ESR values of the external capacitors.
The output voltage drop is the load current times the output
resistance, and the power efficiency is
DS100137-26
FIGURE 2. Voltage Inverting Principle
Application Information
Simple Negative Voltage Converter
The main application of LM828 is to generate a negative
supply voltage. The voltage inverter circuit uses only two
external capacitors as shown in the Basic Application Cir-
cuits. The range of the input supply voltage is 1.8V to 5.5V.
The output characteristics of this circuit can be approximated
by an ideal voltage source in series with a resistance. The
voltage source equals −(V+). The output resistance, R
out
, is
Where I
Q
(V+) is the quiescent power loss of the IC device,
and I
L2
R
out
is the conversion loss associated with the switch
on-resistance, the two external capacitors and their ESRs.
The selection of capacitors is based on the specifications of
the dropout voltage (which equals I
out
R
out
), the output volt-
age ripple, and the converter efficiency. Low ESR capacitors
(following table) are recommended to maximize efficiency,
reduce the output voltage drop and voltage ripple.
