Datasheet

The internal V
L
linear regulator can source over 50mA
to supply the IC, power the low-side gate driver, charge
the external boost capacitor, and supply small external
loads. When driving large FETs, little or no regulator cur-
rent may be available for external loads. For example,
when switched at 600kHz, a single large FET with 18nC
total gate charge requires 18nC x 600kHz = 11mA. To
drive larger MOSFETs, or deliver larger loads, connect
V
L
to an external power supply from 4.75V to 5.5V.
MAX1858
Dual 180° Out-of-Phase PWM Step-Down
Controller with Power Sequencing and POR
_______________________________________________________________________________________ 9
CONVERTER 1
R
S
Q
ILIM1
DL1
PGND
LX1
DH1
BST1
FB1
COMP1
SOFT-START
DAC
SEQUENCING
OSCILLATOR
OSC
SYNC
CK0
V+
5V LINEAR
REGULATOR
V
L
GND
REF
DL2
LX2
DH2
BST2
ILIM2FB2
COMP2
CONVERTER 2
RESET
EN
UVLO
AND
SHUTDOWN
V
REF
2V
MAX1858
RST
V
REF
V
L
Q
V
L
- 0.5V
5
µ
A
Figure 2. Functional Diagram