feature

Low-noise constant-frequency operation under heavy load with high-efficiency pulse skipping (PFM) operation Loaded with adaptive seven-switch configurations (1:3, 1:2, 2:3, 1:1, 3:2, 2:1, 3:1) 92% peak efficiency Input voltage range: 2.7V to 5.5V Output current: 3.3V, VIN = 200mA when VIN=3.6V Output voltage accuracy is ±3% ICC<1µA 1MHz operating frequency in shutdown mode Shutdown Isolates output from input Soft-start limit Inrush current at startup Short-circuit and thermal protection Minimum number of external components No inductor

application

cell phone

handheld computer

Portable RF Communication Equipment

Core power supply for low-power processors

Low voltage DC bus

Digital Signal Processor Power

illustrate

5602 -ic/" title="FAN5602 Product Specifications, Documentation and Source Information" target="_blank">FAN5602 is a general purpose switched capacitor DC/DC converter capable of boost or buck operation. Because of its unique The adaptive fractional switching topology achieves high efficiency over a wider input/output voltage range than any of its predecessors. The FAN5602 utilizes resistive modulation loop control, resulting in lower switching noise than other topologies. Depends on actual load conditions , the device automatically switches between constant frequency and pulse skipping (PFM) operating modes for extended battery life. The FAN5602 produces a fixed regulated output in the range 2.7V to 5.5V, from any type of voltage source. Efficient - in any Efficiency is achieved at both input/output voltages because the internal logic automatically reconfigures the system to have the best topology possible. Only two 1µF barrel capacitors and one 10µF output capacitor are required. During power-up soft-start, Circuit prevents excessive current being drawn from the power supply. Device is protected against short circuit and over temperature conditions. Fan 5602 provides 3.3V, 4.5V and 5.0V output voltages. 1.5V to 5V range is available upon request. Fan 5602 is available for 8 conductors MSOP and 3x3mm 8-lead MLP packages

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. See "Load Current Capability vs. Input Voltage" in "Typical Performance Characteristics".

DC characteristics

VIN=2.7V to 5.5V, C1=C2=1µF, CIN=COUT=10µF, ENABLE=VIN, TA=-40°C to +85°C, unless otherwise noted. Typical value is TA=25°C.

Function description

The FAN5602 is a high-efficiency, low-noise switched capacitor DC/DC converter capable of step-down operation. It has seven built-in switch configurations. Fan 5602 automatically reconfigures switching for maximum efficiency based on the ratio of input voltage to output voltage. The regulated output is implemented by a linear regulation loop that adjusts the on-resistance of the power transistor so that the charge from the input to the capacitor flying each clock cycle is controlled and equal to the charge required by the load. Current spikes are minimized. At light load, the fan 5602 automatically switches to PFM mode to save energy. Adjustment in PFM mode is achieved by skipping pulses. The linearly regulated loop fan 5602 operates over 10mA at a constant frequency at higher loads. A linear regulation loop consisting of power transistors, feedback (resistive divider), and an error amplifier is used to regulate the output voltage and reduce current spikes. The error amplifier receives feedback as input and generates an error voltage signal. The error voltage signal is then used as the gate voltage to adjust the on-resistance power transistor of the power transistor, so an output where charge transfer is controlled from input to output is achieved. Since the charge transfer is controllable, the ESR peak of FAN5602 is small.

switch configuration

The FAN5602 has seven built-in switch configurations including 1:1, 3:2, 2:1, 3:1 buck, 2:3, 1:21:3 boost. When 1.5x VOUT>VIN>VOUT, the 1:1 mode is as shown. Use 1(a). In this mode, the internal oscillator is turned off. The power transistors connecting the input and output into a pass transistor and its gate voltage are controlled through a linear regulation loop, and the remaining power transistors are turned off. In this mode, the fan 5602 operates with a low dropout (LDO) regulator and the output ripple is in the microvolt range. When 1.5 x VOUT>VIN>VOUT, the display 2:3 mode (incremental) is used in Figure 1(b). During the charging phase, two flying capacitors are connected in series, and each capacitor is charged to half the input voltage. During the pumping phase, the flying capacitors are placed in parallel. The input is connected to the bottom of the capacitor so that the voltage at the top of the capacitor is boosted by VIN/2+VIN, which is 3/2 x VIN. By connecting the top of the capacitor to the output, the output can ideally be charged to 3/2 x VIN. If 3/2 x VIN is higher than required, the linear regulation loop will adjust the on-resistance to reduce the voltage. The increased voltage increases the energy efficiency by a factor of 3/2 by connecting the bottom of the capacitor to 3/2×VIN and the top of the capacitor. In 2:3 mode, the ideal power efficiency is VOUT/1.5 x VIN (for example, if VIN=2V, VOUT=2 x VIN=4V, the ideal power efficiency is 100%.

When 2 x VIN > VIN > 1.5 x VIN, the 1:2 mode (acceleration) is used as shown in Figure 1(c). Two flying capacitors are placed in parallel during the charging and pumping phases. During the charging phase, the capacitor is charged to the input voltage. During the pumping phase, the input voltage is placed at the bottom of the capacitor. On top of the capacitor is the VIN raised to 2x. By connecting the top of the capacitor to the output, an ideal charge output to 2 times the VIN. Increasing the voltage at the top of the capacitor to 2Vin increases the power efficiency by a factor of 2. In 1:2 mode the power efficiency is VOUT/2 x VIN (for example, VIN=2V, VOUT=2 x VIN=4V, the ideal power efficiency is 100%. When 3 x VIN>VIN>2 x VIN is displayed when the 1:3 mode (acceleration) is used in Figure 1(d). During the charging phase two flying capacitors are placed side by side, each charged to the VIN. The two flying capacitors are connected in series at the input terminals to the bottom of the series capacitor. The top of the series capacitor is increased to 3 times the VIN. The ideal power efficiency is increased by 3 times, equal to VOUT/3VIN (for example, VIN=1V, VOUT=3x VIN=3V, ideal power Efficiency is 100%. By connecting the output to the top capacitor of the series connected, one can charge the output to 3 times the VIN. The FAN5602's internal logic monitors the input and output and compares them and automatically selects the switch configuration for maximum efficiency .

Buck modes 3:2, 2:1 and 3:1 can be understood as reversing the VIN and VOUT functions discussed above. The reason so many modes are built in is to improve power efficiency and extend battery life. For example, if VOUT=5V, mode 1:2 requires minimum VIN = 2.5V built-in 1:3 mode, the minimum battery voltage is extended to 1.7V. The power transistors used in light-load operation charge pumps are large in size. The switching dynamic loss of the power converter is not small, and the proportion of the total loss increases the power consumption when the load becomes lighter. For power saving when the load is less than 10mA, the constant frequency of FAN5602 switching mode to pulse skip mode (PFM) 2: 3 (3:2), 1:2 (2:1) and 1:3 (3:1), Except for mode 1:1. In PFM the mode linear loop is disabled and the error amplifier is turned off. The PFM comparator is used to set the output threshold and lower threshold. When the output falls below the lower threshold, the oscillator is turned on and the charge pump continues to operate from input to output until the output higher charge exceeds the upper limit. Then turn off the oscillator, turn off the power transistor, and remove the charge from the output capacitor. PFM operation is not used in mode 1:1 even at light loads. Mode 1:1 in the fan 5602 is designed to turn off the oscillator's LDO. The power transistor mode of the LDO is not switched, so there is no dynamic loss. Switching from linear operation to PFM mode (ILOAD < 10mA) and from PFM to linear mode (ILOAD > 10mA) is automatically and constantly monitored based on the load current.

short circuit

When the output voltage is lower than 150mV, the fan 5602 enters the short circuit state. In this case all power transistors are turned off. The shorted small transistor input and output turn on and charge the output. This transistor works all the time as long as the output voltage is <150mV. Since then the transistors are small and the current from input to output is limited. Once the short circuit on the output is removed the transistor is large enough to respond above 150mV, then the fan 5607 enters a soft-start period. The soft-start fan 5602 uses constant current to filter low-pass charging to generate ramps. The ramp is used as a reference voltage during startup. Because the ramp rises slowly from zero and the output follows the ramp, the inrush current is limited. When the ramp is higher than the bandgap voltage, the bandgap voltage replaces the ramp as the reference when the soft-start ends. Soft start takes about 500 microseconds. Thermal Shutdown If the temperature at the connection exceeds 150°C, there is a 15°C lag.

application information

Driving the LCD Backlight with the Fan 5602 The FAN5602 4.5 volt option is ideal for driving the backlight and blinking LEDs of any portable device. A FAN5602 device can supply about 150mA needed to power both the backlight and blinking LEDs. Even thinking that drawing so much current from the fan 5602 would knock the part out of the 3% output regulation, it's not a problem. The backlight and blinking LEDs will still be able to produce optimal brightness when dimmed. when? To build this circuit, be sure to use ceramic capacitors for low ESR. At the same time, all capacitors should be as close as possible to the FAN5602 in the PCB layout. Below is an example circuit for a backlight/flash application.