Mu lt i-Ou t p u t , Lo w -No is e P o w e r-S u p p ly
Co n t ro lle rs fo r No t e b o o k Co m p u t e rs
____________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(Circuit of Figure 1, 3A Table 1 components, T = +25°C, unless otherwise noted.)
A
VL REGULATOR OUTPUT VOLTAGE
vs. OUTPUT CURRENT
SWITCHING FREQUENCY
vs. LOAD CURRENT
5.00
4.98
4.96
4.94
4.92
1000
100
+5V, V = 15V
IN
10
1
+3.3V, V = 15V
IN
+3.3V, V = 6V
IN
V
= 15V
+5V, V = 6V
IN
IN
ON3 = ON5 = 0V
4.90
0.1
0
10
20
30
40
50
60
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
LOAD CURRENT (mA)
0–MAX1635
REF OUTPUT VOLTAGE
vs. OUTPUT CURRENT
START-UP WAVEFORMS
2.510
2.505
RUN
5V/div
2.500
2.495
2.490
3.3V OUTPUT
2V/div
TIME
5V/div
5V OUTPUT
5V/div
2.485
2.480
V
= 15V
IN
ON3 = ON5 = 0V
2ms/div
0
1
2
3
4
5
6
SEQ = VL, 0.015µF CAPACITOR ON-TIME
OUTPUT CURRENT (mA)
__________________________________________________________________________P in De s c rip t io n
PIN
1
NAME
CSH3
CSL3
FUNCTION
Current-Sense Input for the 3.3V SMPS. Current-limit level is 100mV referred to CSL3.
Current-Sense Input. Also serves as the feedback input in fixed-output mode.
2
Feedback Input for the 3.3V SMPS; regulates at FB3 = REF (approx. 2.5V) in adjustable mode. FB3 is a
Dual Mode input that also selects the 3.3V fixed output voltage setting when tied to GND. Connect FB3
to a resistor divider for adjustable-output mode.
3
4
FB3
12OUT
(MAX1630/
32/33/35)
12V/120mA Linear Regulator Output. Input supply comes from V . Bypass 12OUT to GND with
DD
1µF minimum.
Logic-Control Input for secondary feedback. Selects the PWM that uses a transformer and secondary
feedback signal (SECFB):
STEER
(MAX1631/
MAX1634)
STEER = GND: 3.3V SMPS uses transformer
STEER = VL: 5V SMPS uses transformer
6
_______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
