Rainbow Electronics MAX782 - Manual (Page 18)

MAX782
Triple-Output Power-Supply
Controller for Notebook Computers
18 ______________________________________________________________________________________
Because this ramp is applied to the current-limit circuit,
the actual time for the output voltage to ramp up
depends on the load current and output capacitor
value. Using Figure 1’s circuit with a 2A load and no
SS capacitor, full output voltage is reached about
600µs after ON_ is driven high.
Boost Capacitors (C4, C5)
Capacitors C4 and C5 store the boost voltage and pro-
vide the supply for the DH3 and DH5 drivers. Use 0.1µF
and place each within 10mm of the BST_ and LX_ pins.
Boost Diodes (D1A, D1B)
Use high-speed signal diodes; e.g., 1N4148 or equivalent.
Bypass Capacitors
Input Filter Capacitors (C1, C13)
Use at least 3µF/W of output power for the input filter
capacitors, C1 and C13. They should have less than
150m
Ω
ESR, and should be located no further than
10mm from N1 and N2 to prevent ringing. Connect
the negative terminals directly to PGND. Do not
exceed the surge current ratings of input bypass
capacitors.
VPP and VDD Bypass Capacitors (C10, C11, C12)
Use 2.2µF for VDD, and 1µF for VPPA and VPPB.
Table 3. Surface-Mount Components
(See Figure 1 for schematic diagram and Table 4 for phone numbers.)
EC11FS1 Nihon Fast-recovery high voltage diode D2
Sprague
Sprague
Sprague
Sprague
Murata-Erie
1N4148SMTN diodes (fast recovery)
33µF, 35V tantalum capacitors
LR2010-01-R020-F IRC 0.020 Ω , 1% (SMT) resistor R2
LR2010-01-R025-F IRC 0.025 Ω , 1% (SMT) resistor R1
Si9410DY Siliconix N-channel MOSFETs (SO-8) N1-N4
CDR125-100 Sumida 10µH, 2.65A inductor L1
EC10QS04 Nihon 1N5819 SMT diodes D3, D4
BAW56 Philips D1A, D1B
595DD225X0025B2B 2.2µF, 25V tantalum capacitor C12
595DD105X0035A2B 1µF, 35V tantalum capacitors C10, C11
GRM42-6X7R103K50V Murata-Erie 0.01µF, 16V ceramic capacitors C8, C9
595D157X0010D2B Sprague 150µF, 10V tantalum capacitors C7, C14
595D337X0010R2B Sprague 330µF, 10V tantalum capacitor C6
GRM42-6X7R104K50V 0.1µF, 16V ceramic capacitors C4, C5
595D475X0016A2B 1µF, 20V tantalum capacitor C3
595D475X0016A2B 4.7µF, 16V tantalum capacitor C2
595D336X0035R2B Sprague C1, C13
PART NO. MANUFACTURER SPECIFICATION COMPONENT
Coiltronics
Transpower Technologies
Transformer (for 5.5V, 200kHz operation)
PC40EEM12.7/13.7-A160
BEM12.7/13.7-118G
FEM12.7/13.7-A
8 turns #24 AWG
18 turns #26 AWG TDK
TDK
TDK
Custom Transformer:
Core Set
Bobbin
Clamp
Primary
Secondary L2
CTX03-12062-1 Coiltronics
CTX03-12067-1
TTI5870 Transformer (these two have different
sizes and pinouts)