MAX8770GTL+T Maxim Integrated Products, MAX8770GTL+T Datasheet - Page 21

• Manufacturer Part Number: MAX8770GTL+T
• Description: IC CTLR PS 2/1PH QUICK PWM 40QFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8770GTL+T

• Applications: Controller, Intel IMVP-6
• Voltage - Input: 4 ~ 26 V
• Number Of Outputs: 1
• Voltage - Output: 0.125 ~ 1.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PWM Controller for IMVP-6+ CPU Core Power Supplies
phase operation by alternately triggering the main and
secondary phases after the error comparator drops
below the output voltage set point.
The two phases in the MAX8770/MAX8771/MAX8772
operate 180° out-of-phase to minimize input and output
filtering requirements, reduce electromagnetic interfer-
ence (EMI), and improve efficiency. This effectively low-
ers component count—reducing cost, board space,
and component power requirements— making the
MAX8770/MAX8771/MAX8772 ideal for high-power,
cost-sensitive applications.
Typically, switching regulators provide power using
only 1 phase instead of dividing the power among sev-
eral phases. In these applications, the input capacitors
must support high instantaneous current requirements.
The high RMS ripple current can lower efficiency due to
I
effective series resistance (ESR). Therefore, the system
typically requires several low-ESR input capacitors in
parallel to minimize input voltage ripple, to reduce ESR-
related power losses, and to meet the necessary RMS
ripple current rating.
With the MAX8770/MAX8771/MAX8772, the controller
shares the current between two phases that operate
180° out-of-phase, so the high-side MOSFETs never
turn on simultaneously during normal operation. The
instantaneous input current of either phase is effectively
halved, resulting in reduced input voltage ripple, ESR
power loss, and RMS ripple current (see the Input
Capacitor Selection section). Therefore, the same per-
formance may be achieved with fewer or less-expen-
sive input capacitors.
The Quick-PWM controller requires an external +5V
bias supply in addition to the battery. Typically, this
+5V bias supply is the notebook’s 95% efficient +5V
system supply. Keeping the bias supply external to the
IC improves efficiency and eliminates the cost associat-
ed with the +5V linear regulator that would otherwise be
needed to supply the PWM circuit and gate drivers. If
stand-alone capability is needed, the +5V bias supply
can be generated with an external linear regulator.
The +5V bias supply must provide V
troller) and V
current drawn is:
CONFIDENTIAL INFORMATION – RESTRICTED TO INTEL
I
Industry, Inc.
2
2
R® power loss associated with the input capacitor’s
R is a registered trademark of instruments for Research and
I
BIAS
MAX8770/MAX8771/MAX8772 Dual-Phase, Quick-
Dual 180° Out-of-Phase Operation
= I
DD
+5V Bias Supply (V
CC
(gate-drive power), so the maximum
______________________________________________________________________________________
- f
SW
(Q
G(LOW)
+ Q
G(HIGH)
CC
CC
(PWM con-
and V
)
DD
)
where I
Table, f
and Q
charge specification limits at V
V
source is a fixed +4.5V to +5.5V supply. If the +5V
bias supply is powered up prior to the battery supply,
the enable signal (SHDN going from low to high) must
be delayed until the battery voltage is present to
ensure startup.
Connect a resistor (R
the switching period T
where C
A 96.75kΩ to 303.25kΩ corresponds to switching peri-
ods of 167ns (600kHz) to 500ns (200kHz), respectively.
High-frequency (600kHz) operation optimizes the appli-
cation for the smallest component size, trading off effi-
ciency due to higher switching losses. This may be
acceptable in ultra-portable devices where the load
currents are lower and the controller is powered from a
lower voltage supply. Low-frequency (200kHz) opera-
tion offers the best overall efficiency at the expense of
component size and board space.
The core of each phase contains a fast, low-jitter,
adjustable one-shot that sets the high-side MOSFETs
on-time. The one-shot for the main phase varies the on-
time in response to the input and feedback voltages.
The main high-side switch on-time is inversely propor-
tional to the input voltage (V
feedback voltage (V
where the switching period (T
resistor at the TON pin, and 0.075V is an approximation
to accommodate the expected drop across the low-
side MOSFET switch.
The one-shot for the secondary phase varies the on-
time in response to the input voltage and the difference
between the main and secondary inductor currents.
Two identical transconductance amplifiers integrate the
difference between the master and slave current-sense
signals. The summed output is internally connected to
IN
and V
G(HIGH)
CC
SW
TON
DD
is provided in the Electrical Characteristics
is the switching frequency, and Q
t
= 16.26pF.
T
ON MAIN
can be tied together if the input power
SW
are the MOSFET data sheet’s total gate-
(
= C
Switching Frequency (TON)
FB
)
®
TON
TON
SW
=
):
IMVP-6 LICENSEES
T
) between TON and V
SW
= 1/f
(R
(
IN
TON
V
FB
SW
SW
), and proportional to the
GS
V
On-Time One-Shot
IN
+
, per phase:
+ 6.5kΩ)
= 1/f
= 5V.
0 075
.
SW
V
)
) is set by the
IN
G(LOW)
to set
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