Part Number: MAX1044ESA+T

Manufacturer: Analog Devices Inc./Maxim Integrated


Shipped from: Shenzhen/HK Warehouse

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MAX1044ESA+T General Description

Monolithic CMOS switched-capacitor voltage converters like the MAX1044 and ICL7660 can multiply, divide, or invert a positive input voltage. They share pinouts with standard-issue components like the ICL7660 and LTC1044. From 1.5V to 10V, the operation is guaranteed without needing an external diode, which is valid for all operating temperatures. The loss in voltage at the output is only 0.5V, and they can supply 10mA. A smaller external capacitor can be used with the MAX1044 because of its BOOST pin, which increases the oscillator frequency beyond the audible range. The MAX1044/ICL7660 has minimal quiescent current and very high efficiency. Four power MOSFET switches and an oscillator control circuit are integrated into a single chip. For example, a -5V supply can be generated to power analog circuitry from a +5V logic supply. The MAX660 provides up to 100mA with a voltage drop of less than 0.65V, making it ideal for power-hungry applications.

MAX1044ESA+T Features

  • Miniature μMAX Package
  • Energy Supply Voltage from 1.5V to 10.0V.
  • Typical efficiency of 98% in converting power.
  • Adjust the Input Voltage by a Factor of 2, 2, 4, or 4.
  • The switching frequencies are raised by the BOOST pin (MAX1044).
  • At no load, the maximum supply current is 200 A (or 5V).
  • There is no need for an additional diode while working at higher voltages.

MAX1044ESA+T Applications

  • -5V Supply from +5V Logic Supply
  • Personal Communications Equipment
  • Portable Telephones
  • Op-Amp Power Supplies
  • EIA/TIA-232E and EIA/TIA-562 Power Supplies
  • Data-Acquisition Systems
  • Handheld Instruments
  • Panel Meters

Detailed Description

To convert voltages, the MAX1044/ICL7660 uses a charge pump. To store energy, they use a bucket capacitor to store charge before moving it to a larger reservoir capacitor. In Figure 2, we see the corresponding operation of an ideal voltage inverter circuit. Switches S1 and S3 are closed, and S2 and S4 are opened at the beginning of each cycle, connecting the bucket capacitor C1 across V+ and charging it.

The positive terminal of C1 is connected to the ground during the second half of each cycle when switches S2 and S4 are closed and switches S1 and S3 are opened. This links the reservoir capacitor C2 to the first capacitor, C1. Whenever the potential difference between capacitors (C1 and C2) is smaller than that between C1 and G, current will flow from C1 to C2 to bring the potentials between the two capacitors into equilibrium. In subsequent cycles, C1 will keep feeding charge into C2 until the voltage across C2 drops to – (V+). The output of an absolute voltage inverter is less than – (V+) due to the resistance of the switches S1-S4 and the load draining charge from C2. More details on the MAX1044/ICL7660 can be gleaned through a simulation of a switched-capacitor circuit. Resistance can be artificially created by rerouting C1, a bucket capacitor between the circuit’s input and output.

● Design Information

When a few low-power components require negative or doubled supply voltages, the MAX1044/ICL7660 is intended to serve as a straightforward, space-saving, and inexpensive solution to this problem.

● Proper Use of the Low-Voltage (LV) Pin

Using the LV pin, you can bypass this regulator, increasing its performance at low voltages and letting it function at as low as 1.5V. For low-voltage operation and compatibility with the industry-standard LTC1044 and ICL7660, the LV pin must be connected to the ground for supply voltages lower than 3.5V. Still, it must be left open for supply voltages of more than 3.5V. This is necessary for low-voltage operations.

Under any situation of operation, the LV pin of the MAX1044 can be grounded. Increased oscillator frequency and improved low-voltage performance are two advantages of this design. The quiescent current will be higher, and the efficiency will be lower at higher supply voltages. This is a drawback. If the supply voltage exceeds 5V, the LV pin on the Maxim ICL7660 must be left unconnected. When running at low supply voltages with the LV open, BOOST the connections to the LV, and OSC pins should be kept as short as possible or shielded to minimize electromagnetic interference (EMI) from generating oscillator jitter.

● Oscillator Frequency Considerations

Regular operation requires leaving the BOOST and OSC pins of the MAX1044/ICL7660 open and utilizing the oscillator’s frequency set to its nominal value. When the frequency is raised, the amount of output resistance, audio interference, voltage ripple, and the required size of capacitors are all reduced. Bringing down the frequency brings the quiescent current down, bringing the efficiency up.

● Oscillator Frequency Specifications

The MAX1044 and the ICL7660 do not come with an accurate oscillator frequency. For the MAX1044, only the minimum values of 1 kHz and 5 kHz, and for the ICL7660, the typical value of 10 kHz is mentioned. If it is necessary to have a specific oscillator frequency, you should drive the OSC pin with an external oscillator.

● Output Voltage Considerations

The MAX1044/ICL7660 does not have a controlled voltage on its output. The load will cause a variation in the output voltages, which is proportional to the output resistance. The oscillator frequency and the capacitor’s value are the primary factors determining the output resistance. The temperature as well as the supply voltage both affect the oscillator’s frequency. For instance, the output resistance is typically 50 ohms when using charge-pump capacitors rated at ten fF and an input voltage of 5 volts. Therefore, the output voltage is approximate -5V when light loads are present, but it drops to approximately -4.5V when a load current of 10mA is present. Some analog circuits are susceptible to damage from even minute fluctuations in the supply voltage, which are irrelevant to digital circuitry.

Therefore, when utilizing the MAX1044/ICL7660 for powering sensitive analog circuits, it is necessary to consider those circuits’ power-supply rejection ratio. Under heavy loads, the output ripple, as well as the output drop, will increase. If required, the output impedance of the MAX1044 and ICL7660 can be lowered by paralleling devices, increasing the capacitance of C1 and C2, or connecting the BOOST pin of the MAX1044 to V+ to raise the oscillator frequency.


The MAX1044ESA+T is an 8-pin NSOIC-packaged, monolithic CMOS switching capacitor voltage converter. These voltage converters, called charge pumps, work by storing energy in a “bucket” capacitor before moving it to a “reservoir” capacitor. A positive input voltage can be inverted, multiplied, divided, or halved. Similar to the regular ICL7660 and LTC1044 devices, it features pin compatibility with them.

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