feature

Peak efficiency>85%

Low EMI

low ripple

Output voltage 1.3V/1.8V

Input Voltage Range: 2.2V to 5.5V

Output Current: Up to 250mA

Output voltage accuracy ±2.5%

30 microamp operating current

ICC<1µA in shutdown mode

2 MHz operating frequency

Shutdown isolates output from input

Soft Start Limits Inrush Current

Short circuit and thermal protection

Minimum number of external components

6-lead 3x3mm MLP package

application

cell phone

handheld computer

Portable Electronic Devices

Core Supply for Next Generation Processors

Low voltage DC bus

digital camera

Digital Signal Processor Power

illustrate

The FAN5601 is an advanced third generation switched capacitor using Fairchild's proprietary step-down DC/DC converter ScalarPump™ technology. This innovative architecture utilizes scalar switch reconfiguration and fractional switching techniques to produce low output ripple, low ESR peaking and improved efficiency over a wide load range. Fan 5601 generates input voltage from 2.2V to 5V. Custom output voltages are available to increase from 1 volt to 1.8 volts in increments of 100 volts. Please contact Marketing for custom output. To maximize efficiency, the FAN5601 implements regulation by skipping pulses. The size of the switch is dynamically scaled according to the load current, therefore, current peaks and EMI are minimized. An internal soft-start circuit prevents excessive current draw from the power supply. The device is internally protected against short circuit and overheating conditions. Fan 5601 has 6 leads 3x3mm MLP. ScalarPump™ is a registered trademark of Fairchild Semiconductor Corporation.

notes:

1. Operation beyond the absolute maximum ratings may cause permanent damage to the device.

2. Using Mil Standard 883E, Method 3015.7 (Human Body Model) and EIA/Jesd222C101-A (Charging Device Model).

3. One square inch, 1oz bottom side ground plane, connected to top side ground plane through via field.

Electrical Characteristics

VIN=2.2V to 5.5V, IOUT=1mA, CB=1μF, CIN=10μF, COUT=10μF, TA=-40°C to +85°C, typical values at TA=25°C unless otherwise noted time measurement.

notes:

4. With the oscillator off, measure the no-load supply current.

5. The purpose of short-circuit protection is to prevent a pre-existing short-circuit condition, ie, an assembly short-circuit. It exists before the device is powered on. The short-circuit current limit is 25 mA on average. Short circuit current normal The on-resistance of the internal device has an inherent limitation on operation. Because this resistance is in the 1Ω range, thermal shutdown may occur in some cases. However, after the first thermal shutdown event, the short-circuit condition will be considered pre-existing and the load current will be reduced to 25Ma average.

Detailed description

The automatic control of the FAN5601 switched capacitor DC/DC converter configures the switch to achieve high efficiency and provides regulated output voltage through pulse skipping, pulse frequency modulation (PFM). An internal soft-start circuit prevents excessive inrush current from the power supply. Each switch is divided into three segments. Based on the VIN value, an internal circuit determines the segment used to reduce current peaks. Buck Charge Pump Operation The 2:1 configuration shown in Figure (a) is enabled when VIN ≥ 2.22 × VOUT. The factor 0.9 is used instead of 1 to account for the switching sum to accommodate the hysteresis of the voltage detector comparator. Two-phase non-overlapping clock signals are generated to drive the four switches. When switches 1 and 3 are on, switches 2 and 4 are off and CB is charged. When switches 2 and 4 are on, switches 1 and 3 are off and the charge is transferred from CB to Coot. The 1:1 configuration shown in Figure (B) is enabled when VIN < 2.22 × VOUT. In a 1:1 configuration, switch 3 is always off and switch 4 is always on. At 1.6V output the setting configuration changes from 2:1 to 1:1 at VIN=3.56V. Changes at VIN=3.06 at 1.3V output setting

Pulse skip PFM and fractional switching operation When the output voltage reaches the upper limit, the switch is turned off when the output voltage reaches the lower limit. Considering the buck 2:1 operating mode, a 1.6V output is for example, when the output reaches about 1.62V (upper limit), the control logic turns off all switches. The switch stops completely. This is pulse skip mode. Because the power supply is isolated from the output, the output voltage will drop. Once the output is down to about 1.58V (lower limit), the device will return to the normal switching mode when each switch is turned on a quarter of the time first. The other quarter of each switch will be turned on if you don't reach the prescribed cycle when your third charge arrives. Full-switching operation is only during start-up or under heavy-load conditions, when half-switching operation cannot achieve regulation within seven charge cycles. Soft Start The soft start feature limits inrush current and is enabled during initial equipment operation. The reference voltage is used to control the rate at which the output voltage rises to its final value. Typical startup time is 1 ms. Since the rate ramping of the output voltage is controlled by an internally generated slow ramp, pulse skipping occurs and the magnetizing inrush current is automatically limited.

Shutdown, UV Low, Short Circuit Current Limit, and Thermal Shutdown The device has an active low shutdown pin to reduce supply current to less than 1µA. In shutdown mode, power is disconnected from the output. The UVLO is triggered when the supply voltage is below 2V. When the output voltage is lower than 150mV, a trigger short circuit protection. In this mode, 15 out of 16 pulses during switching will be skipped and supply current is limited. Thermal shutdown is triggered at 150°C.

2:1 Configuration Switch Reversing Charge Phase All Pumping Phase Switches Class C B Section 1 S3 S3 S4 VIN Ground Class C + Guarantee Cocos Out

1:1 configuration switch 3 always off switch 4 always on switch 1 and 2 in phase 1 reverse switch 1 and 2 position phase 2

Application Information: Proper operation of the Fan 5601 requires a ceramic barrel capacitor in the 0.1µF to 1µF range; a 10µF output bypass capacitor and a 10µF input bypass capacitor. For best output ripple and noise performance, the use of low ESR (<0.05Ω) ceramic input and output bypass capacitors is recommended. X5R and X7R rated capacitors provide adequate performance over the -40°C to 85°C temperature range. The value of the barrel capacitor depends on the load current requirement. 1µF barrel capacitors will work well at all load currents in all applications, 0.1µF capacitors will support most applications at 100mA load currents. The selection of the actual application should verify that the barrel capacitor value is at the lowest input voltage and highest load current. Thirty percent To account for tolerances, it is recommended to use a safety margin of barrel capacitance and on-resistance variation of the internal switch.

One of the main advantages of the ScalarPump™ architecture is that the dynamically scaled resistance of the switch reduces the peak current in the barrel capacitor and therefore the input and output ripple currents. Nonetheless, these current spikes produce voltage spikes on the input and output pins due to the ESR of the input and output bypass capacitors. However, these ESR peaks can be easily filtered because their frequency is 12 times the clock frequency. In applications where conducted and radiated EMI/RFI interference must be as low as possible, the user may consider additional input and output filtering. For example, adding an LC filter to a standard output bypass configuration is very effective in reducing output ripple and voltage nails. The diagram shows an LC filter inductor and 1µF capacitor using a 100nH chip. Channel 1 of the figure shows the ripple voltage output by the device when channel 2 shows the ripple voltage output by the filter when VIN=3.3V,

VOUT=1.3V, IOUT=100mA. Similar filtering methods greatly reduce current peaks at the input. The user should be aware that the resistive voltage drop in the inductor is connected in series in the input and output leads.

Effect of LC Filter on Output Ripple When evaluating the FAN5601 (or any other switched capacitor DC-DC converter) the user should take care to keep the power source impedance low; lead inductance and resistive losses should be avoided with long wires causing high. A careful layout of the ground plane is necessary because the current spikes when the barrel capacitors are discharged. Input and output bypass capacitors should be placed as close as possible to the device pins.