MAX1775 Maxim, MAX1775 Datasheet - Page 9

• Manufacturer Part Number: MAX1775
• Description: Dual-Output Step-Down DC-DC Converter for PDA/Palmtop Computers
• Manufacturer: Maxim

PIN
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
DC-DC Converter for PDA/Palmtop Computers
SHDNM
SHDNC
NAME
PGND
NDRV
PDRV
GND
CVH
FBM
CS+
CVL
REF
FBC
LXC
INC
CS-
IN
_______________________________________________________________________________________
Shutdown for Main Regulator. A low voltage on SHDNM shuts off the main output. For normal
operation, connect SHDNM to IN.
Shutdown for Core Regulator. A low voltage on SHDNC shuts off the core output. For normal operation,
connect SHDNC to CVL.
Power Ground. Ground for NDRV and core output synchronous rectifier. Connect all grounds together
close to the IC.
N-Channel Drive Output. Drives the main output synchronous rectifier MOSFET. NDRV swings between
CVL and PGND.
Low-Side Regulator Bypass. CVL is the output of an internal LDO regulator. This is the internal power
supply for the device control circuitry as well as the N-channel driver. Bypass CVL with a 1.0µF or
greater capacitor to GND. When CS- is above the CVL switchover threshold (2.47V), CVL is powered
from the main output.
Power Supply Input
P-Channel Drive Output. Drives the main output high-side MOSFET switch. PDRV swings between IN
and CVH. The voltage at CVH is regulated at V
High-Side Drive Bypass. CVH is the output of an internal LDO regulator with respect to V
low-side of the P-channel driver output. Bypass with a 1.0µF capacitor or greater to IN. When the input
voltage is less than +5.5V, CVH is switched to PGND.
Reference Voltage Output. Bypass REF to GND with a 0.22µF or greater capacitor.
Main Output Feedback. Connect FBM to a resistive voltage-divider to set main output voltage between
+1.25V to +5.5V.
Main Regulator High-Side Current-Sense Input. Connect the sense resistor between CS+ and CS-.
This voltage is used to set the current limit and to turn off the synchronous rectifier when the inductor
current approaches zero.
Main Regulator Low-Side Current-Sense Input. Connect CS- to the main output.
Core Output Feedback. Connect FBC to a resistive voltage-divider to set core output between +1.0V to
+5.0V.
Analog Ground
Core Supply Input
Core Converter Switching Node
Dual-Output Step-Down
FUNCTION
IN
- 4.3V unless the input voltage is less than 5.5V.
Pin Description
IN
. This is the
9