Rainbow Electronics MAX1791 - Manual (Page 11)

MAX1762/MAX1791
High-Efficiency, 10-Pin µMAX, Step-Down
Controllers for Notebooks
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VP Input and VL Logic Supply
An internal linear regulator supplied by VP produces
the +4.65V supply (VL) that powers the PWM controller,
logic, reference, and other blocks within the
MAX1762/MAX1791. This +4.65V low-dropout linear
regulator can supply up to 25mA for external loads.
Bypass VL to GND with at least a 1µF ceramic capaci-
tor. V
VP can range between 5V and 20V. VL is turned
off when the device is in shutdown and drops by
approximately 500mV during a fault condition, such as
when the output is short circuited to ground, and recov-
ers when SHDN is cycled or power is reset. If VL is not
driven externally, then V
VP should be at least 5V to
ensure operation. If V VP is running from a 5V (±10%)
supply, V
VP
should be externally connected to VL.
Table 2. Component Manufacturers
MANUFACTURER USA PHONE WEBSITE INFO
Coiltronics 561-241-7876 www.coiltronics.com
Fairchild Semiconductor 408-822-2181 www.fairchildsemi.com
Sanyo 619-661-6835 www.secc.co.jp
USA 847-956-0666
Sumida
Japan 81-3-3607-5111
www.sumida.com
Taiyo Yuden 408-573-4150 www.t-yuden.com
Figure 5. Functional Block Diagram
Q1
Q2
OUT
GND
DH DH
DRIVER
C OUT
VP
DL
DL
DRIVER
TON
1-SHOT
TRIG Q
ON-TIME
COMPUTE
ON/OFF
CONTROL
2V
V REF
TIMER
C VL
C IN
VOS
-100mV
CS
ILIM
LINEAR
REG
FEEDBACK
MUX
(FIGURE 9)
1-SHOT
T ON
T OFF
TRIG
VL
C REF
REF
REF
OUT
FB
REF
-30%
FB
VL OUT
V IN VP
VP
OUT
VP
UVP
LATCH
S
R
Q
Q
Q
S
R
Q
MAX1762
MAX1791
SHDN
10 Ω
1 µF