Rainbow Electronics MAX17008 - Manual (Page 26)

MAX17007A/MAX17008
Internal Integration
An integrator amplifier forces the DC average of the FB
voltage to equal the target voltage. This internal amplifier
integrates the feedback voltage and provides a fine
adjustment to the regulation voltage (Figure 4), allowing
accurate DC output-voltage regulation regardless of the
compensated feedback ripple voltage and internal slope-
compensation variation. The integrator amplifier has the
ability to shift the output voltage by ±140mV (typ).
The MAX17007A/MAX17008 disable the integrator by
connecting the amplifier inputs together at the begin-
ning of all dynamic REFIN1 transitions done in pulse-
skipping mode. The integrator remains disabled until
20μs after the transition is completed (the internal target
settles) and the output is in regulation (edge detected
on the error comparator).
Power-Good Outputs (PGOOD)
and Fault Protection
PGOOD_ is the open-drain output that continuously
monitors the respective output voltage for undervoltage
and overvoltage conditions. The respective PGOOD_ is
actively held low in shutdown (EN_ = GND) during soft-
start and soft-shutdown. Approximately 200μs (typ)
after the soft-start terminates, PGOOD_ becomes high
impedance as long as the respective output voltage is
in regulation.
PGOOD1 goes low if the output voltage drops 200mV
below the target voltage (REFIN1 or fixed 1.05V), or
rises 300mV above the target voltage (REFIN1 or fixed
1.05V), or the SMPS1 controller is shut down.
In adjustable mode, PGOOD2 goes low if the feedback
voltage drops 100mV below the target voltage (0.7V), or
rises 150mV above the target voltage (0.7V), or the
SMPS2 controller is shut down. In preset mode (fixed
1.5V), the PGOOD2 thresholds are -200mV and +300mV.
For a logic-level PGOOD output voltage, connect an
external pullup resistor between PGOOD and V
DD . A
100k
Ω pullup resistor works well in most applications.
See Figure 13.
Overvoltage Protection (OVP, MAX17007A Only)
When the internal feedback voltage rises above the
overvoltage threshold, the OVP comparator immediate-
ly pulls DH low and forces DL high, pulls PGOOD low,
sets the fault latch, and disables the faulted SMPS con-
troller. Toggle EN or cycle V
CC power below the V CC
POR to clear the fault latch and restart the controller.
The overvoltage thresholds are +300mV for SMPS1
(fixed 1.05V and adjustable REFIN1), +300mV for
SMPS2 in preset mode (fixed 1.5V output), and +150mV
for SMPS2 in adjustable mode (0.7V feedback).
An OV fault on one side does not affect the other side.
Dual and Combinable QPWM Graphics
Core Controllers for Notebook Computers
26 ______________________________________________________________________________________
TARGET
+ V
OVP
TARGET
- V
UVP
CSL OR FB
FAULT
OVP ENABLED
(MAX17007A ONLY)
FAULT
LATCH
ONE
SHOT
200 μs
POWER-GOOD
IN
CLK
OUT
OVP
UVP
EN
SOFT-START
COMPLETE
NOTE: ONLY THE MAX17007A HAS
OVP FUNCTION ENABLED.
Figure 13. Power-Good and Fault Protection