MAX17020ETJ+T Maxim Integrated Products, MAX17020ETJ+T Datasheet - Page 19

• Manufacturer Part Number: MAX17020ETJ+T
• Description: IC CTLR PWM DUAL STEP DN 32-TQFN
• Manufacturer: Maxim Integrated Products
• Series: Quick-PWM™r

Specifications of MAX17020ETJ+T

• Applications: Power Supplies
• Current - Supply: 1mA
• Voltage - Supply: 6 V ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX17020 step-down controller is ideal for high-
voltage, low-power supplies for notebook computers.
Maxim’s Quick-PWM pulse-width modulator in the
MAX17020 is specifically designed for handling fast
load steps while maintaining a relatively constant oper-
ating frequency and inductor operating point over a
wide range of input voltages. The Quick-PWM architec-
ture circumvents the poor load-transient timing prob-
lems of fixed-frequency current-mode PWMs, while also
avoiding the problems caused by widely varying
switching frequencies in conventional constant-on-time
and constant-off-time PWM schemes. Figure 2 is a
functional diagram overview. Figure 3 is the functional
diagram—Quick-PWM core.
The MAX17020 includes several features for multipur-
pose notebook functionality, allowing this controller to
be used two or three times in a single notebook—main,
I/O chipset, and graphics. The MAX17020 includes a
100mA LDO that can be configured for preset 5V oper-
ation—ideal for initial power-up of the notebook and
main supply—or can be adjusted for lower voltage
operation—ideal for low-power I/O or graphics supply
requirements. Additionally, the MAX17020 includes a
3.3V, 5mA RTC supply that remains always enabled,
which can be used to power the RTC supply and sys-
tem pullups when the notebook shuts down. The
MAX17020 also includes an optional secondary feed-
back input that allows an unregulated charge pump or
secondary winding to be included on a supply—ideal
for generating the low-power 12V to 15V load switch
supply. Finally, the MAX17020 includes a reference
input on SMPS 2 that allows dynamic voltage transitions
when driven by an adjustable resistive voltage-divider or
DAC—ideal for the dynamic graphics core requirements.
The MAX17020 includes a low-current (5mA) linear reg-
ulator that remains active as long as the input supply
(IN) exceeds 2V (typ). The main purpose of this
“always-enabled” linear regulator is to power the real-
time clock (RTC) when all other notebook regulators are
disabled. RTC also serves as the main bias supply of
the MAX17020 so it powers up before the LDO and
switching regulators. The RTC regulator sources at
least 5mA for external loads.
______________________________________________________________________________________
Detailed Description
Dual Quick-PWM Step-Down Controller
with Low-Power LDO, RTC Regulator
3.3V RTC Power
The MAX17020 includes a high-current (100mA) linear
regulator that can be configured for preset 5V or 3.3V
operation or adjusted between 0.6V to 4V. When the
MAX17020 is configured as a main supply, this LDO is
required to generate the 5V bias supply necessary to
power up the switching regulators. Once the switching
regulators are enabled, the LDO can be bypassed
using the dedicated BYP input. The adjustable linear
regulator allows generation of the 3.3V suspend supply
or buffered low-power chipset and GPU reference sup-
plies. The MAX17020 LDO sources at least 100mA of
supply current.
The MAX17020 includes an independent LDO bypass
input that allows the LDO to be bypassed by either
switching regulator output or from a different regulator all
together. When the bypass voltage (BYP) exceeds 93.5%
of the LDO output voltage for 500μs, the MAX17020
reduces the LDO regulation threshold and turns on an
internal p-channel MOSFET to short BYP to LDO. Instead
of disabling the LDO when the MAX17020 enables the
bypass switch, the controller reduces the LDO regulation
voltage, which effectively places the linear regulator in a
standby state while switched over, yet allows a fast
recovery if the bypass supply drops.
Connect BYP to GND when not used to avoid uninten-
tional conduction through the body diode (BYP to LDO)
of the p-channel MOSFET.
The MAX17020 requires an external 5V bias supply
(V
5V bias supply is generated by either the internal
100mA LDO (when configured for a main supply) or
from the notebook’s 95%-efficient 5V main supply (when
configured for an I/O chipset, DDR, or graphics).
Keeping these bias supply inputs independent
improves the overall efficiency and allows the internal
linear regulator to be used for other applications as well.
The V
vers and the V
control blocks. The maximum current required is domi-
nated by the switching losses of the drivers and can be
estimated as follows:
I
BIAS(MAX)
DD
and V
DD
bias supply input powers the internal gate dri-
Adjustable 100mA Linear Regulator
CC
= I
) in addition to the battery. Typically, this
CC(MAX)
CC
bias supply input powers the analog
5V Bias Supply (V
+ f
SW
Q
G
≈ 30mA to 60mA (typ)
Bypass Switch
CC
/V
DD
19
)