HA16114 View Datasheet(PDF) - Renesas Electronics

Part Name

Description

Manufacturer

HA16114

Switching Regulator for Chopper Type DC/DC Converter

Renesas Electronics 

HA16116FP/FPJ, HA16121FP/FPJ

The triangle wave is a voltage waveform used as a reference in creating a PWM pulse. This block operates

according to the following principles. A constant current IO, determined by an external timing resistor RT, is

made to flow continuously to external timing capacitor CT. When the CT pin voltage exceeds the

comparator threshold voltage VH, the comparator output causes a switch to operate, discharging a current IO

from CT. Next, when the CT pin voltage drops below threshold voltage VL, the comparator output again

causes the switch to operate, stopping the IO discharge. The triangle wave is generated by this repeated

operation.

Note that IO = 1.1 V/RT. Since the IO current mirror circuit has a very limited current producing ability, RT

should be set to ≥ 5 kΩ (IO ≥ 220 µA).

With this IC series, VH and VL of the triangle wave are fixed internally at about 1.6 V and 1.0 V by the

internal resistors RA, RB, and RC. The oscillator frequency can be calculated as follows.

fOSC =

1

t1 + t2 + t3

Here,

t1 =

CT ⋅ (VH − VL)

1.1 V/RT

= CT RT ⋅ (VH − VL)

1.1 V

t2 =

CT ⋅ (VH − VL)

(2 − 1) × 1.1 V/RT

=

CT RT ⋅ (VH − VL)

1.1 V

=

t1

VH − VL = 0.6 V

t1 = t2 =

0.6

1.1

CT RT

t3 ≈ 0.8 µs (comparator delay time in the oscillator)

Accordingly,

fOSC ≈

1

2t1 + t3

≈

1

1.1 CT RT + 0.8 µs

[Hz]

Note that the value of fOSC may differ slightly from the above calculation depending on the amount of delay

in the comparator circuit. Also, at high frequencies this comparator delay can cause triangle wave

overshoot or undershoot, skewing the dead band threshold. Confirm the actual value in implementation

and adjust the constants accordingly.

Rev.2.0, Sep.18.2003, page 8 of 33

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