FAN8038C 데이터 시트보기 (PDF) - Fairchild Semiconductor
부품명
상세내역
일치하는 목록
FAN8038C Datasheet PDF : 16 Pages
| |||
FAN8038C
6. DC-DC CONVERTER CONTROL CIRCUIT
6-1. Set to output voltage
• The DC-DC converter output voltage, SVCC1, is set by internal resistors R3 and R4 and the voltage, SVCC1, is defined as
follows.
SVCC1 = (1+ R3)1.267 = 2.5[V ]
R4
• This voltage, SVCC1, can be varied with the addition of an external resistors R1 and R2 as shown Figure.2 and the voltage
is defined as follows.
R1⋅ R3 + R2 ⋅ R4
SVCC 1
=
R1 +
R3
R2
⋅
R2
R4
+
R4
× 1.267[V
]
R2 + R4
• Where, R1 and R2 are exteranl resistors, and R3 and R4 are internal resistors.
VBAT
2
8
CSCP
6
10uA
1.25V
Short Circuit Protection
7
SVCC1
12
R3
R1
Error Amp
1.267V
65KΩ
R2
R3 = 30 KΩ
R4
R4 = 30.5KΩ
5
SVCC1
1.267V
PWM
Comp
Triangular
Waveform
9
COSC
4
CDEDSET
34
3
Figure 2. Schematic of DC-DC Converter
6-2. Power-on Reset function
• If the output voltage of DC-DC conver, SVCC1,is over than 90%, the RSTOUT(pin3) goes from low level to high level, and
RST (pin34) goes to high level to low level. The reset voltage has 50mV of hysteresis to prevent output chattering.
6-3. Delayed Short Circuit Protection
• When the error amplifier output (pin6) become high level state during the abnormal conditions such as over load or short
ciruit, the exteral capacitor, CSCP, is charged, and when the SCP (pin8) voltage reaches 1.25V(typ.), the PWM comparator
output, BDSW(pin5), is shwitch-off.
11
Share Link: 