Rainbow Electronics MAX1855 - Manual (Page 13)

MAX1716/MAX1854/MAX1855
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
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Pin Description (continued)
PIN NAME FUNCTION
21 SKIP
Pulse-Skipping or Low-Noise Mode Control Input. Connect to V CC for low-noise forced-PWM mode.
Connect to GND to enable pulse-skipping operation. Low-noise forced-PWM mode causes inductor
current recirculation at light loads and suppresses pulse-skipping operation. Normal operation
prevents current recirculation. SKIP can also be used to disable both overvoltage and undervoltage
protection circuits and clear the fault latch (see No-Fault Test Mode). Do not leave
SKIP floating.
22 BST
Boost Flying-Capacitor Connection. Connect to an external capacitor and diode according to the
standard application circuit (Figure 1).
23 LX
External Inductor Connection. Connect LX to the switched side of the inductor. LX serves as the
lower supply rail for the DH high-side gate driver. LX does not connect to the current-limit
comparator.
24 CS
Current-Sense Input. Connect a resistor (R SENSE ) between CS and PGND. The current-limit
threshold is set by ILIM. If the current-sense signal (Inductor Current ✕ R SENSE ) exceeds the
current-limit threshold, the MAX1716/MAX1854/MAX1855 will not initiate a new cycle.
COMPONENT
CIRCUIT 1
(FIGURE 1)
CIRCUIT 2
(FIGURE 11)
CIRCUIT 3
(FIGURE 12)
CIRCUIT 4
(FIGURE 13)
Output Voltage 1.6V 1.3V 1.0V 1.6V
Input Voltage Range 7V to 24V 7V to 24V 7V to 24V 7V to 24V
M axi m um Load C ur r ent 18A 12A 12A 18A
Inductor
0.68 µH
Sumida
CDEP134H-0R6
or Panasonic
ETQP6F0R6BFA
1 µH
Sumida
CEP125-1R0MC
or Panasonic
ETQP6FIRIBFA
0.68 µH
Sumida
CDEP134H-0R6
or Panasonic
ETQP6F0R6BFA
0.47 µH
Sumitomo
CXE-R47
TON Level Float Float REF GND
Frequency 300kHz 300kHz 400kHz 550kHz
High-Side MOSFET
International Rectifier
(2) IRF7811
International Rectifier
IRF7811
International Rectifier
IRF7811
International Rectifier
(2) IRF7811
Low-Side MOSFET
Fairchild (2) FDS7764A
Or International
Rectifier (2) IRF7811
Fairchild (2) FDS7764A
Or International
Rectifier (2) IRF7811
Fairchild (2) FDS7764A
Or International
Rectifier (2) IRF7811
Fairchild (2) FDS7764A
Or International
Rectifier (2) IRF7811
Input Capacitor
(5) 10 µF
Taiyo Yuden
TMK432BJ106
(4) 10 µF
Taiyo Yuden
TMK432BJ106
(4) 10 µF
Taiyo Yuden
TMK432BJ106
(5) 10 µF
Taiyo Yuden
TMK432BJ106
Output Capacitor
(5) 220 µF
Panasonic
EEFUE0E221R
(4) 220 µF
Panasonic
EEFUE0E221R
(4) 220 µF
Panasonic
EEFUE0E221R
(8) 47 µF
Taiyo Yuden
JMK432BJ476MM
or TDK
C4532X5ROJ476M
Current-Sense Resistor 3m Ω 3.5m Ω 3.5m Ω 3m Ω
ILIM Level V REF /3 V REF /4 V REF /4 V REF /3
Voltage-Positioning
Resistor Ratio
1:1 (0.5x) 1:2 (0.66x) 1:2 (0.66x) 1:1 (0.5x)
Table 1. Component Selection for Standard Applications