HA16114P Datasheet, PDF (6/38 Pages) Hitachi Semiconductor – Switching Regulator for Chopper Type DC/DC Converter

HA16114P/PJ/FP/FPJ, HA16120FP/FPJ
Guide to the Functional Description
The description covers the topics indicated below.
Oscillator
1. ^frequency
(f_OSC) control and
synchronization
DC/DC output
2.
voltage setting
and error
amplifier usage
3.
Dead-band and
soft-start settings
Output stage and
4. power MOS FET
driving method
GND*¹ 1
SYNC 2
R_T 3
C_T 4
IN(−) 5
E/O 6
IN(+) 7
P.GND*¹ 8
16 Vref
15 ADJ
14 DB
13 ON/OFF
12 TM
11 CL(−)
10 V_IN
9 OUT
(Top view)
Vref adjustment,
undervoltage
5. lockout, and
overcurrent
protection
6. ^{ON/OFF pin}
usage
Intermittent
7.
mode timing
during
overcurrent
8.
Setting of
current limit
Note: 1. 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 Ω. The I_O current mirror has a limited current capacity, so R_T should be at least
5 kΩ (I_O ≤ 220 µA).
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.
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