HIP5020 datasheet(13/15 Pages) INTERSIL

13 / 15 page

2-25

The charge pump can be used to supply current for external

loads on the VCC pin. Figure 11 shows the regulation

characteristics of the charge pump in the various operating

regions. These characteristics are for a DC-DC converter

(Circuit 3) operating at 100kHz and with 1

µF capacitors for C4

and C5. The charge pump may not be suitable for some

applications and external loads. Be sure that the load can

tolerate the VCC voltage variation with input voltage. During

Hysteretic Mode, the external load should be removed when

the converter turns off. Note that the charge pump and

oscillator are disabled with RUN low (see Operating Modes).

The external load could cause an under-voltage lockout trip

and subsequent soft-start cycle.

Light Load Power Dissipation

The converter efficiency and power dissipation at light load is

mainly a function of the bias supplied to the HIP5020. Figure

12 shows the input current as a function of the input voltage

for the two states of the RUN signal. IIN is summation of both

the current into the VIN and VINF pins. The curve for IIN with

the RUN signal High does not include the gate drive power.

The gate drive power is a function of the MOSFETs gate

charge, voltage and switching frequency. Figure 13 shows

the combined gate energy required by the internal

MOSFETs with the charge pump characteristics. To

determine the total bias power:

1. Multiply the value in Figure 13 by the switching frequency.

2. Add the product of the voltage and current from the RUN

= High curve in Figure 12.

3. Multiply by the ratio of RUN time to the Hysteretic period.

4. Add the product of the voltage and current from the RUN

= Low curve in Figure 12.

MOSFET On-Resistance

Conduction losses are a signiﬁcant portion of the power

dissipation in a DC-DC converter. The HIP5020 conduction

losses are the product of the square of the average output

current and the MOSFET on-resistance - rDS(ON). The

rDS(ON) of the MOSFETs is a function of VCC and junction

temperature. VCC changes with the input voltage as shown

in Figure 10 above. Figure 14 shows the maximum rDS(ON)

of both MOSFETs as a function of input voltage for a junction

temperature of 25oC. The junction temperature of the

HIP5020 also effects rDS(ON). Figure 15 shows the rDS(ON)

as a function of temperature for three gate voltage levels.

INPUT VOLTAGE (V)

FIGURE 10. CHARGE PUMP REGULATOR INPUT VOLTAGE

CHARACTERISTICS

CHARGE

PUMP

DISABLED

REGULATION

REGION

VOLTAGE

DOUBLER

REGION

100

EXTERNAL LOAD (MADC)

FIGURE 11. BIAS VOLTAGE (VCC) vs EXTERNAL LOAD

CURRENT

VIN = 5VDC

VIN = 12VDC

VIN = 8.65VDC

CIRCUIT 3

100

VIN (V)

FIGURE 12. BIAS POWER CHARACTERISTICS

RUN = LOW

RUN = HIGH

CT - GND

VIN (V)

0.4

0.3

0.2

0.1

0.0

FIGURE 13. MOSFET GATE ENERGY CHARACTERISTICS vs

INPUT VOLTAGE

HIP5020

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