HIP6004E is a step-down synchronous rectification PWM controller and output voltage supervisor. HIP6004E integrates PWM control, output voltage regulation, voltage monitoring and overvoltage, in a very small package (SOIC-20 or TSSOP-20). With functions such as overcurrent protection, the output voltage can be precisely adjusted in increments of 25mV within the range of DC 1.050 to 1.825V. At the same time, it also has the characteristics of soft start, wide adjustable working frequency, remote control switch, fast dynamic response, large output power, and good voltage stability. These advantages make HIP6004E widely used in high-performance microprocessor power supply (such as early intel Pentium Ⅲ and other microprocessors) and high-power DC/DC converters and low-voltage distributed power supply systems. It adopts 20-pin SOIC-20 or TSSOP-20 packaging technology, and can be interchanged with RT9224E .

Figure 1 Resistance vs Frequency

Figure 2 Bias Supply Current vs Frequency

Initial function description

HIP6004E automatically initializes upon receiving power. No special sequencing of input power is necessary. The power-on reset (POR) function continuously monitors the input supply voltage. POR monitors the bias voltage on the VCC pin and the input voltage (VIN) on the OCSET pin. The upper level OCSET is equal to a fixed voltage drop less than VIN (see current protection). The power-on reset function initiates soft-start after both input supply voltages run above their POR thresholds. To operate with a single + 12V supply, VIN and VCC are equivalent +12V supplies must exceed the VCC rising threshold before power-on reset begins to operate.

Soft-start The power-on reset function initiates a soft-start sequence. An internal 10µA current source charges an external capacitor (CSS) on the SS pin to 4V. The soft-start clamps the error amplifier output (COMP pin) and the reference input (+error amplifier terminal) to the SS pin voltage. Figure 3 shows a soft-start interval with CSS=0.1µF. Initially the clamp (COMP pin) in the error amplifier controls the output voltage of the converter. At t1 in Figure 3, the SS voltage reaches the valley of the oscillator's triangle wave. The oscillator's triangle wave is compared to the ramped error amplifier voltage. This produces phase pulses of increasing width to charge the output capacitor(s). This increases the pulse width interval to continue t2. The reference input clamp controls the output voltage as long as there is sufficient output voltage. This is the interval between t2 and t3 in the network connection gure 3. The voltage at T3SS exceeds the DACOUT voltage and the output voltage is in regulation. This method provides a fast and controlled rise of the output voltage. When the PGOOD signal is toggled "high", the output voltage (VSEN pin) is within ±10% ofDACOUT. The built-in power-good 2% hysteretic comparator prevents PGOOD from oscillating due to nominal output voltage ripple.

Figure 3 Soft-start interval

overcurrent protection

The overcurrent protection function monitors the current from the short-circuit converter by using the on-resistance r output DS(ON) of the upper MOSFET. This approach increases converter efficiency and reduces cost by eliminating current-sense resistors. The overcurrent function is cycled in a soft-start function in hiccup mode to provide fault protection. Resistor (ROCSET) programs the overcurrent trip level. The internal 200µA current chip develops the voltage OCSET across R which is referenced to VIN. When the voltage across the upper MOSFET (also referenced to VIN) exceeds the voltage OCSET across R, the overcurrent protection function initiates a soft-start sequence. The soft-start function discharges ?SS with a 10µA current sink and inhibits PWM operation. Soft-start charging functions CSS and PWM operation resumes with the error amplifier clamped to the SS voltage. If an overload occurs while charging ?SS, the soft-start function inhibits PWM operation while fully charging ?SS to 4V to complete its cycle. Figure 4 illustrates this operation with an overload condition. Note that the inductor current increases beyond 15A during the CSS billing interval causing the overcurrent protection to travel. The converter consumes very little power using this method. The input power for this measurement is 2.5W for the condition of Figure 4.

The overcurrent function will trip at the peak inductor current (Ipeak) as determined by:

OCSET is the internal OCSET current source (200µA typical). The change of OC travel point is mainly due to the change of MOSFET's ?DS(ON). To avoid overcurrent tripping within the normal operating load range, connect the th rOCSET resistor from the above equation: 1. Maximum RDS(ON) at maximum junction temperature. 2. Minimum residual OCSET from a specific network cation table. 3. Make sure I PEAK is IPEAK > IOUT(max) + (?I) ?2, where ?I is the output inductor ripple current. For the formula for the ripple current see the Section Component Guide titled "Selecting the Output Inductor". A small ceramic capacitor should be placed in parallel with ROCSET to smooth the voltage across ROCSET to the input voltage in the presence of switching noise.

Output voltage programming

The output voltage of a HIP6004E converter is programmed at discrete levels between 1.05V DC and 1.825VDC. The voltage identification (VID) pin programs the internal voltage reference (DACOUT) with a TTL-compatible 5-bit digital-to-analog converter (DAC). The DACOUT level also sets the PGOOD and OVP thresholds. The DACOUT voltages specified in Table 1 are used to connect 32 different combinations of pins on the VID field. The output voltage should not be adjusted while the converter is supplying power. Disconnect the input power before changing the output voltage. The PGOOD signal can be switched with motion overvoltage protection during regulation of the output voltage operation.

Figure 4. Overcurrent Operation

Table 1