HA16120 RENESAS [Renesas Technology Corp], HA16120 Datasheet - Page 6

• Manufacturer Part Number: HA16120
• Description: Switching Regulator for Chopper Type DC/DC Converter
• Manufacturer: RENESAS [Renesas Technology Corp]

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
Guide to the Functional Description
The description covers the topics indicated below.
Note: 1.
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
is fed continuously to an external timing capacitor C
threshold voltage V
to flow from C
closes the switching transistor, stopping the 3I
sawtooth wave.
The value of I
5 kΩ (I
Internal resistances R
approximately 1.6 V and 1.0 V.
Rev.2.0, Sep.18.2003, page 6 of 37
1.
2.
3.
4.
Oscillator
frequency
(f
synchronization
DC/DC output
voltage setting
and error
amplifier usage
Dead-band and
soft-start settings
Output stage and
power MOS FET
driving method
OSC
O
≤ 220 µA).
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.
) control and
O
T
is 1.1 V/R
. When the C
TH
A
, the comparator output opens a switching transistor, allowing a 3I
, R
B
T
, and R
Ω. The I
P.GND*
GND*
SYNC
T
IN(+)
IN( )
C
pin voltage drops below a threshold voltage V
E/O
set the peak and valley voltages V
R
C
1
T
T
1
O
current mirror has a limited current capacity, so R
1
2
3
4
5
6
7
8
(Top view)
O
discharge. Repetition of these operations generates a
T
. When the C
16
15
14
13
12
11
10
9
O
determined by an external timing resistor R
Vref
ADJ
DB
ON/
TM
CL( )
V
OUT
IN
TH
OFF
and V
T
pin voltage exceeds a comparator
TL
of the sawtooth waveform at
TL
5.
6.
7.
8.
, the comparator output
Vref adjustment,
undervoltage
lockout, and
overcurrent
protection
ON/
usage
Intermittent
mode timing
during
overcurrent
Setting of
current limit
O
T
OFF
should be at least
discharge current
pin
T