
HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
6
Guide to the Functional Description
The description covers the topics indicated below.
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
GND*
1
SYNC
R
T
C
T
IN(
)
E/O
IN(+)
P.GND*
1
Vref
ADJ
DB
ON/
OFF
TM
CL(
)
V
IN
OUT
1.
2.
3.
4.
5.
6.
7.
8.
Oscillator
frequency
(f ) control and
synchronization
DC/DC output
voltage setting
and error
amplifier usage
Dead-band and
soft-start settings
Output stage and
power MOS FET
driving method
Vref adjustment,
undervoltage
lockout, and
overcurrent
protection
Intermittent
mode timing
during
overcurrent
Setting of
current limit
(Top view)
Note: 1.
ON/
OFF
pin
usage
P.GND is a high-current (
±
1 A maximum peak) ground pin connected to the totem-pole output circuit.
GND is a low-current ground pin connected to the Vref voltage reference. Both pins must be grounded.
1. Sawtooth Oscillator (Triangle Wave)
1.1 Operation and Frequency Control
The sawtooth wave is a voltage waveform from which the PWM pulses are created (See figure 1). The
sawtooth oscillator operates as follows. A constant current I
O
determined by an external timing resistor R
T
is fed continuously to an external timing capacitor C
T
. When the C
T
pin voltage exceeds a comparator
threshold voltage V
TH
, the comparator output opens a switching transistor, allowing a 3I
O
discharge current
to flow from C
T
. When the C
T
pin voltage drops below a threshold voltage V
TL
, the comparator output
closes the switching transistor, stopping the 3I
O
discharge. Repetition of these operations generates a
sawtooth wave.
The value of I
O
is 1.1 V/R
T
. The I
O
current mirror has a limited current capacity, so R
T
should be at least
5 k
(I
O
≤
220
μ
A).
Internal resistances R
A
, R
B
, and R
C
set the peak and valley voltages V
TH
and V
TL
of the sawtooth waveform
at approximately 1.6 V and 1.0 V.