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PDF SGM3206 Data sheet ( Hoja de datos )
| Número de pieza | SGM3206 | |
| Descripción | Unregulated 60mA Charge Pump Voltage Inverter | |
| Fabricantes | Shengbang Microelectronics | |
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Preliminary Datasheet for Engineering Sample
SGM3206
Unregulated 60mA
Charge Pump Voltage Inverter
GENERAL DESCRIPTION
The SGM3206 generates an unregulated negative output
voltage from an input voltage ranging from 1.4V to 5.5V.
The device is typically supplied by a pre-regulated supply
rail of 5V or 3.3V. Due to its wide input voltage range, two
or three NiCd, NiMH, or alkaline battery cells, as well as
one Li-ion cell can also power them.
Only three external capacitors are required to build a
complete DC/DC charge pump inverter. Assembled in a
small package, the complete converter can be built on a
50mm2 board area. Additional board area and component
count reduction is achieved by replacing the Schottky
diode that is typically needed for start-up into load by
integrated circuitry.
The SGM3206 can deliver a maximum output current of
60mA with a typical conversion efficiency of greater than
90% over a wide output current range. The fixed
switching frequency is 50kHz.
FEATURES
Inverts Input Supply Voltage
Up to 60mA Output Current
Input Voltage Range from 1.4V to 5.5V
Quiescent Current: 120μA
Integrated Active Schottky Diode for Start-Up into
Load
-40℃ to +85℃ Operating Temperature Range
Available in Green SOT-23-5 Package
APPLICATIONS
LCD Bias
GaAs Bias for RF Power Amps
Sensor Supply in Portable Instruments
Bipolar Amplifier Supply
The SGM3206 is available in SOT-23-5 package. It
operates over an ambient temperature range of -40℃ to
+85℃.
TYPICAL APPLICATION
CFLY
3.3μF
INPUT
1.4V to 5.5V
CIN
3.3μF
3
CFLY-
5
CFLY+
2
IN
SGM3206 OUT 1
GND
4
SG Micro Corp
www.sg-micro.com
OUTPUT
-1.4V to -5.5V, 60mA MAX
COUT
3.3μF
April 10, 2013
1 page  
SGM3206
DETAILED DESCRIPTION
Operating Principle
The SGM3206 charge pump inverts the voltage applied
to the input. For the best performance, use low equivalent
series resistance (ESR) capacitors (e.g., ceramic).
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor CFLY charges to
the voltage at VIN. During the second half-cycle, S1 and
S3 open and S2 and S4 close. This connects the positive
terminal of CFLY to GND and the negative to VOUT. By
connecting CFLY in parallel, COUT is charged negative. The
actual voltage at the output is more positive than -VIN,
since switches S1 - S4 have resistance and the load
drains charge from COUT.
VIN
S1
CFLY
3.3μF
S4
VOUT (-VIN)
S2 S3
COUT
3.3μF
GND
GND
Figure 1. Operating Principle
Charge Pump Output Resistance
The SGM3206 device is not voltage regulator. The
charge pump output source resistance is approximately
9Ω at room temperature (with VIN = 5V), and VOUT
approaches 5V when lightly loaded. VOUT will droop
toward GND as load current increases.
VOUT = -(VIN - ROUT × IOUT)
ROUT
1
fOSC CFLY
4
2RSWITCH ESRCFLY
ESRCOUT
where, ROUT = output resistance of the converter.
Unregulated 60mA
Charge Pump Voltage Inverter
Efficiency Considerations
The power efficiency of a switched-capacitor voltage
converter is affected by three factors: the internal losses
in the converter IC, the resistive losses of the capacitors,
and the conversion losses during charge transfer
between the capacitors. The internal losses are
associated with the IC’s internal functions, such as
driving the switches, oscillator, etc. These losses are
affected by operating conditions such as input voltage,
temperature, and frequency. The next two losses are
associated with the voltage converter circuit’s output
resistance. Switch losses occur because of the
on-resistance of the MOSFET switches in the IC. Charge
pump capacitor losses occur because of their ESR. The
relationship between these losses and the output
resistance is as follows:
PCAPACITOR LOSSES + PCONVERSION LOSSES = IOUT2 × ROUT
where: RSWITCH = resistance of a single MOSFET-switch
inside the converter
fOSC = oscillator frequency
The first term is the effective resistance from an ideal
switched-capacitor circuit. Conversion losses occur
during the charge transfer between CFLY and COUT when
there is a voltage difference between them. The power
loss is:
P CONVERSION LOSS
1
2
CFLY
VIN2
V2
OUT
1
2
COUT
V2
RIPPLE
2VOUT VRIPPLE
fOSC
The efficiency of the SGM3206 is dominated by their
quiescent supply current at low output current and by
their output impedance at higher current.
IOUT
IOUT IQ
1
IOUT ROUT
VIN
where, IQ = quiescent current.
SG Micro Corp
www.sg-micro.com
5
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