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MAX16831ATJ+ ,High-Voltage, High-Power LED Driver with Analog and PWM Dimming ControlFeaturesThe MAX16831 is a current-mode, high-brightness LED♦ Wide Input Range: 6V to 76V With Cold- ..
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MAX4475ASA ,SOT23 / Low-Noise / Low-Distortion / Wide-Band / Rail-to-Rail Op AmpsApplications Available in Space-Saving SOT23, µMAX, andTSSOP PackagesADC BuffersDAC Output Amplif ..
MAX4475ASA+ ,SOT23, Low-Noise, Low-Distortion, Wide-Band, Rail-to-Rail Op AmpsELECTRICAL CHARACTERISTICS(V = +5V, V = 0V, V = 0V, V = V /2, R tied to V /2, SHDN = V , T = -40°C ..
MAX1682EUK-T-MAX1683EUK-T
Switched-Capacitor Voltage Doublers
General DescriptionThe ultra-small MAX1682/MAX1683 monolithic, CMOS
charge-pump voltage doublers accept input voltages
ranging from +2.0V to +5.5V. Their high voltage-con-
version efficiency (over 98%) and low operating current
(110µA for MAX1682) make these devices ideal for
both battery-powered and board-level voltage-doubler
applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. The MAX1682 operates
at 12kHz and the MAX1683 operates at 35kHz. A typi-
cal application includes generating a 6V supply to
power an LCD display in a hand-held PDA. Both parts
are available in a 5-pin SOT23 package and can deliver
30mA with a typical voltage drop of 600mV.
________________________ApplicationsSmall LCD Panels
Cell Phones
Handy-Terminals
PDAs
____________________________Features5-Pin SOT23 Package+2.0V to +5.5V Input Voltage Range98% Voltage-Conversion Efficiency110µA Quiescent Current (MAX1682)Requires Only Two CapacitorsUp to 45mA Output Current
MAX1682/MAX1683
Switched-Capacitor Voltage Doublers
Pin Configuration
Typical Operating Circuit19-1305; Rev 1; 8/98
MAX1682/MAX1683
Switched-Capacitor Voltage Doublers
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN= +5.0V, capacitor values from Table 2, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
ELECTRICAL CHARACTERISTICS(VIN= +5.0V, capacitor values from Table 2, TA= -40°C to +85°C, unless otherwise noted.) (Note 3)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Note 2:Once started, the MAX1682/MAX1683 typically operate down to 1V.
Note 3:Specifications at -40°C to +85°C are guaranteed by design.
IN to GND.................................................................+6V to -0.3V
OUT to GND.......................................................+12V, VIN- 0.3V
OUT Output Current............................................................50mA
Output Short-Circuit Duration.................................1sec (Note 1)
Continuous Power Dissipation (TA= +70°C)
SOT23-5 (derate 7.1mW/°C above +70°C)...................571mW
Operating Temperature Range
MAX1682EUK/MAX1683EUK...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Note 1:Avoid shorting OUT to GND, as it may damage the device. For temperatures above +85°C, shorting OUT to GND even
instantaneously will damage the device.
MAX1682/MAX1683
Switched-Capacitor Voltage Doublersypical Operating Characteristics(Typical Operating Circuit, VIN= +5V, C1 = C2 = 10µF for the MAX1682 and 3.3µF for the MAX1683, TA= +25°C, unless otherwise
noted.)
MAX1682/MAX1683
Switched-Capacitor Voltage Doublers
Typical Operating Characteristics (continued)(Typical Operating Circuit, VIN= +5V, C1 = C2 = 10µF for the MAX1682 and 3.3µF for the MAX1683, TA= +25°C, unless otherwise
noted.)
_______________Detailed DescriptionThe MAX1682/MAX1683 capacitive charge pumps
double the voltage applied to their input. Figure 1
shows a simplified functional diagram of an ideal volt-
age doubler. During the first half-cycle, switches S1
and S2 close, and capacitor C1 charges to VIN. During
the second half cycle, S1 and S2 open, S3 and S4
close, and C1 is level shifted upward by VINvolts. This
connects C1 to the reservoir capacitor C2, allowing
energy to be delivered to the output as necessary. The
actual voltage is slightly lower than 2 x VIN, since
switches S1–S4 have resistance and the load drains
charge from C2.
Charge-Pump OutputThe MAX1682/MAX1683 have a finite output resistance
of about 20Ω(Table 2). As the load current increases,
the devices’ output voltage (VOUT) droops. The droop
equals the current drawn from VOUTtimes the circuit’s
output impedance (RS), as follows:
VDROOP= IOUTx RS
VOUT= 2 x VIN- VDROOP
Efficiency ConsiderationsThe 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 total power loss is:
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:
where fOSCis the oscillator frequency. The first term is
the effective resistance from an ideal switched-
capacitor circuit (Figures 2a and 2b).
MAX1682/MAX1683
Switched-Capacitor Voltage DoublersFigure 2a. Switched-Capacitor Model
Figure 1. Simplified Functional Diagram of Ideal Voltage
Figure 2b. Equivalent Circuit
MAX1682/MAX1683Conversion losses occur during the charge transfer
between C1 and C2 when there is a voltage difference
between them. The power loss is:
where VRIPPLEis the peak-to-peak output voltage ripple
determined by the output capacitor and load current
(see Output Capacitorsection). Choose capacitor val-
ues that decrease the output resistance (see Flying
Capacitor section).
Applications Information
Flying Capacitor (C1)To maintain the lowest output resistance, use capaci-
tors with low ESR. Suitable capacitor manufacturers are
listed in Table 1. The charge-pump output resistance is
a function of C1 and C2’s ESR and the internal switch
resistance, as shown in the equation for ROUTin the
Efficiency Considerationssection.
Minimizing the charge-pump capacitor’s ESR mini-
mizes the total resistance. Suggested values are listed
in Tables 2 and 3.
Using a larger flying capacitor reduces the output
impedance and improves efficiency (see the Efficiency
Considerationssection). Above a certain point, increas-
ing C1’s capacitance has a negligible effect because
the output resistance becomes dominated by the inter-
nal switch resistance and capacitor ESR (see the
Output Resistance vs. Capacitance graph in the
Typical Operating Characteristics). Table 2 lists the
most desirable capacitor values—those that produce a
low output resistance. But when space is a constraint, it
may be necessary to sacrifice low output resistance for
the sake of small capacitor size. Table 3 demonstrates
how the capacitor affects output resistance.
Output Capacitor (C2)Increasing the output capacitance reduces the output
ripple voltage. Decreasing its ESR reduces both output
resistance and ripple. Smaller capacitance values can
be used with light loads. Use the following equation to
calculate the peak-to-peak ripple:
VRIPPLE= IOUT/ (fOSCx C2) + 2 x IOUTx ESRC2
Input Bypass CapacitorBypass the incoming supply to reduce its AC imped-
ance and the impact of the MAX1682/MAX1683’s
switching noise. When loaded, the circuit draws a con-
tinuous current of 2 x IOUT. A 0.1µF bypass capacitor is
sufficient.
Switched-Capacitor Voltage Doublers
Table 1. Recommended Capacitor Manufacturers
Table 2. Suggested Capacitor Values for
Low Output Resistance
Table 3. Suggested Capacitor Values for
Minimum Size
