MAX17007GTI+ Maxim Integrated Products, MAX17007GTI+ Datasheet - Page 20

• Manufacturer Part Number: MAX17007GTI+
• Description: IC CTRLR QPWM GRAPHICS 28TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17007GTI+

• Applications: Power Supplies
• Current - Supply: 1.7mA
• Voltage - Supply: 4.5 V ~ 26 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX17007/MAX17008 feature independent resis-
tor-programmable switching frequencies for each
SMPS, providing flexibility for applications where one
SMPS operates at a lower switching frequency when
connected to a high-voltage input rail while the other
SMPS operates at a higher switching frequency when
connected to a lower voltage rail as a second-stage
regulator. Connect a resistor (R
V
where C
sponds to switching periods of 1.67µs (600kHz) to 5µs
(200kHz) for SMPS1 and SMPS2. High-frequency
(600kHz) operation optimizes the application for the
smallest component size, trading off efficiency 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 volt-
age supply. Low-frequency (200kHz) operation offers
the best overall efficiency at the expense of component
size and board space.
For continuous conduction operation, the actual switching
frequency can be estimated by:
where V
the inductor discharge path, including synchronous
rectifier, inductor, and printed-circuit board (PCB)
resistances; V
charging path, including the high-side switch, inductor,
and PCB resistances; and t
by the on-time block.
When operating in separate mode, it is recommended
that both SMPS switching frequencies be set apart by
10% to 30% to prevent the two sides from beating
against each other.
In combined mode (FB2 = V
time, and hence the switching frequency, for both SMPS.
The on-time is programmed using the TON1 equation,
which sets the switching frequency per phase. The
effective switching frequency as seen on the input and
output capacitors is twice the per-phase frequency.
Dual and Combinable QPWM Graphics
Core Controllers for Notebook Computers
20
IN
to set the switching period T
______________________________________________________________________________________
DIS
TON
is the sum of the parasitic voltage drops in
T
T
SW1
SW2
= 16.26pF. A 97.5kΩ to 302.5kΩ corre-
CHG
f
SW
Combined-Mode On-Time One-Shot
= C
= C
is the sum of the resistances in the
=
TON
TON
t
ON IN
V
OUT
(
(R
(R
V
ON
TON1
TON2
+
+
CC
is the on-time calculated
TON
SW
V
V
Switching Frequency
DIS
CHG
), TON1 sets the on-
+ 6.5kΩ)
+ 6.5kΩ)
) between TON and
= 1/f
)
SW
:
In combined mode, the one-shot for SMPS2 varies the
on-time in response to the input voltage and the differ-
ence between the SMPS1 and SMPS2 inductor cur-
rents. The SMPS1 one-shot in combined mode behaves
the same way as it does in separate mode. As such,
SMPS2 regulates the current balance, while SMPS1
regulates the voltage.
Two identical transconductance amplifiers integrate the
difference between SMPS1 and SMPS2 current-sense
signals. The summed output is internally connected to
CCI, allowing adjustment of the integration time con-
stant with a compensation network (usually a capacitor)
connected between CCI and the output.
The resulting compensation current and voltage are
determined by the following equations:
where Z
SMPS2 on-time one-shot uses this integrated signal
(V
When SMPS1 and SMPS2 current-sense signals
(V
anced, the transconductance amplifiers adjust the
SMPS2 on-time, which increases or decreases the
SMPS2 inductor current until the current-sense signals
are properly balanced. In combined mode, the SMPS2
on-time is given by:
EN1 and EN2 provide independent control of output
soft-start and soft-shutdown. This allows flexible control
of startup and shutdown sequencing. The outputs can
be started simultaneously, sequentially, or indepen-
dently. To provide sequential startup, connect EN of
one regulator to PGOOD of the other. For example, with
EN1 connected to PGOOD2, OUT1 soft-starts after
OUT2 is in regulation.
When configured in separate mode, the two outputs are
independent. A fault at one output does not trigger
shutdown of the other.
When configured in combined mode (FB2 = V
is the master control input that enables/disables the
combined output, while EN2 has no function and must
be connected to GND. The startup slew rate follows
that of SMPS1.
Toggle EN low to clear the overvoltage, undervoltage,
and thermal-fault latches.
CCI
CSH1
I
) to set the SMPS2 high-side MOSFETs on-time.
CCI
SMPS2 On-Time t
- V
CCI
= G
CSL1
SMPS Enable Controls (EN1, EN2)
is the impedance at the CCI output. The
m
[(V
V
CCI
and V
CSH1
Combined-Mode Current Balance
= V
- V
CSH2
OUT
ON2
CSL1
+ I
= T
- V
) - (V
CCI
CSL2
SW2
Z
CSH2
CCI
(V
) become unbal-
CCI
- V
/V
CSL2
IN
CC
)
)]
), EN1