MAX17021GTL+ Maxim Integrated Products, MAX17021GTL+ Datasheet - Page 24

• Manufacturer Part Number: MAX17021GTL+
• Description: IC CTLR PWM DUAL IMVP-6+ 40-TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17021GTL+

• Applications: Power Supplies
• Current - Supply: 2.5mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 40-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Dual-Phase, Quick-PWM Controllers for
IMVP-6+/IMVP-6.5 CPU Core Power Supplies
The two phases in the MAX17021/MAX17082/
MAX17482 operate 180° out-of-phase to minimize input
and output filtering requirements, reduce electromagnetic
interference (EMI), and improve efficiency. This effectively
lowers component count—reducing cost, board space,
and component power requirements—making the
MAX17021/MAX17082/MAX17482 ideal for high-power,
cost-sensitive applications.
Typically, switching regulators provide power using
only one phase instead of dividing the power among
several phases. In these applications, the input capaci-
tors must support high instantaneous current require-
ments. The high RMS ripple current can lower
efficiency due to I
input capacitor’s effective series resistance (ESR).
Therefore, the system typically requires several low-
ESR input capacitors in parallel to minimize input-volt-
age ripple, to reduce ESR-related power losses, and to
meet the necessary RMS ripple current rating.
With the MAX17021/MAX17082/MAX17482, the con-
troller 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 effec-
tively 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 can be achieved with fewer or less-expensive
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:
where I
table, f
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
24
IN
G(HIGH)
and V
______________________________________________________________________________________
SW
I
CC
BIAS
is the switching frequency, and Q
DD
are the MOSFET data sheet’s total gate-
is provided in the Electrical Characteristics
Dual 180° Out-of-Phase Operation
= I
DD
can be tied together if the input power
+5V Bias Supply (V
CC
(gate-drive power), so the maximum
+ f
2
R power loss associated with the
SW
(Q
G(LOW)
GS
= 5V.
+ Q
G(HIGH)
CC
CC
(PWM con-
G(LOW)
and V
)
DD
and
)
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
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 might 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 TON input includes open-circuit protection to avoid
long, uncontrolled on-times that could result in an over-
voltage condition on the output. The MAX17021/
MAX17082/MAX17482 detect an open-circuit fault if the
TON current drops below 10μA for any reason—the
TON resistor (R
value is used, the input voltage is low, etc. Under these
conditions, the MAX17021/MAX17082/MAX17482 stop
switching (DH_ and DL_ pulled low) and immediately
set the fault latch. Toggle SHDN or cycle the V
power supply below 0.5V to clear the fault latch and
reactivate the controller.
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 as measured by the TON
input, and proportional to the 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
t
ON MAIN
(
T
SW
TON
= 16.3pF x (R
)
=
) is unpopulated, a high resistance
Switching Frequency (TON)
T
TON
SW
SW
(
TON Open-Circuit Protection
) between TON and V
= 1/f
V
FB
V
IN
+
SW
SW
TON
0 075
.
, per phase:
= 1/f
+ 6.5kΩ)
On-Time One-Shot
V
)
SW
) is set by the
IN
FB
to set
):
CC