MAX1636 Maxim, MAX1636 Datasheet - Page 8

• Manufacturer Part Number: MAX1636
• Description: Low-Voltage / Precision Step-Down Controller for Portable CPU Power
• Manufacturer: Maxim

Low-Voltage, Precision Step-Down
Controller for Portable CPU Power
8
The basic MAX1636 buck converter (Figure 1) is easily
adapted to meet a wide range of applications with
inputs up to 30V by substituting components from
Table 1. These circuits represent a good set of trade-
offs between cost, size, and efficiency, while staying
within the worst-case specification limits for stress-
related parameters, such as capacitor ripple current.
Do not change the circuits’ switching frequency without
______________________________________________________________Pin Description
______Standard Application Circuit
9, 10
PIN
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
_______________________________________________________________________________________
RESET
NAME
SHDN
PGND
SYNC
GND
SKIP
CSH
CSL
OVP
REF
V
BST
CC
DH
FB
V+
VL
DL
LX
CC
Current-Sense Input, High Side
Current-Sense Input, Low Side. Also serves as a feedback input in fixed output modes.
Timed Reset Output. Low for at least 100ms after output voltage is valid, then goes high impedance
(open drain).
Shutdown Control Input. Puts chip in shutdown or standby mode, depending on OVP (Table 5).
Overvoltage Protection Enable/Disable. Tie to GND to disable OVP; tie to V
Compensation pin. Connect a small capacitor to GND to set the integration time constant.
1.100V Reference Output. Capable of sourcing 50µA for external loads; bypass with a 0.22µF
(min) capacitor.
Oscillator Frequency Select and Synchronization Input. Tie to V
200kHz operation.
Analog Ground
Feedback Input. Tie to GND for fixed 3.3V output; tie to V
adjustable mode.
Main Supply Voltage Input. Powers the PWM controller, logic, and reference. Input range is +3.15V to
+5.5V.
5V VL Linear-Regulator Input. The VL linear regulator automatically shuts off if V+ is left open or shorted to
V
5V Linear-Regulator Output. Powers the DL low-side gate driver. Bypass with a 2.2µF (min) capacitor.
Low-Side Gate-Driver Output
Power Ground
Boost-Capacitor Connection
High-Side Gate-Driver Output
Inductor Connection
Low-Noise Mode Control. Forces fixed-frequency PWM operation when high.
L
. Bypass V+ to GND with a 0.1µF capacitor close to the IC.
first recalculating component values (particularly induc-
tance value at maximum battery voltage). Adding a
Schottky rectifier across the synchronous rectifier
improves circuit efficiency by approximately 1%. This
rectifier is otherwise not needed because the MOSFET
required typically incorporates a high-speed silicon
diode from drain to source. Use a Schottky rectifier
rated at a DC current equal to at least one-third of the
load current.
FUNCTION
CC
for fixed 2.5V output; tie to resistor divider for
CC
for 300kHz operation; tie to GND for
CC
to enable OVP.