MAX1980ETP+ Maxim Integrated Products, MAX1980ETP+ Datasheet - Page 15

• Manufacturer Part Number: MAX1980ETP+
• Description: IC CNTRLR QUICK-PWM 20-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX1980ETP+

• Pwm Type: Controller
• Number Of Outputs: 1
• Frequency - Max: 550kHz
• Duty Cycle: 50%
• Voltage - Supply: 4 V ~ 28 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: 0°C ~ 85°C
• Package / Case: 20-TQFN Exposed Pad
• Frequency-max: 550kHz
• Input Voltage: 4 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 100 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

(V
phases may sum together, increasing the total input
and output ripple voltage and RMS ripple current.
During in-phase operation, the input capacitors must
support large, instantaneous input currents when the
high-side MOSFETs turn on simultaneously, resulting in
increased ripple voltage and current when compared
to out-of-phase operation. The higher RMS ripple cur-
rent degrades efficiency due to power loss associated
with the input capacitor’s effective series resistance
(ESR). This typically requires a large number of low-
ESR input capacitors in parallel to meet input ripple
current ratings or minimize ESR-related losses.
The polarity select input (POL) determines whether ris-
ing edges (POL = V
trigger a new cycle. For low duty-cycle applications
(duty factor < 50%), triggering on the rising edge of the
master’s low-side gate driver prevents both high-side
MOSFETs from turning on at the same time. Staggering
the phases in this way lowers the input ripple current,
thereby reducing the input capacitor requirements. For
applications operating with approximately a 50% duty
factor, out-of-phase operation (POL = V
slave controller to complete an on-pulse coincident to
the master controller determining when to initiate its
next on time. The noise generated when the slave con-
troller turns off its high-side MOSFET could compro-
mise the master controller’s feedback voltage and
current-sense inputs, causing inaccurate decisions that
lead to more jitter in the switching waveforms. Under
these conditions, triggering off of the falling edge (POL
= GND) of the master’s low-side gate driver forces the
controllers to operate in-phase, improving the system’s
noise immunity.
The MAX1980 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, eliminates power dissipation limitations, and
removes the cost associated with the internal, 5V linear
regulator that would otherwise be needed to supply the
PWM circuit and gate drivers. If standalone capability is
needed, the 5V supply can be generated with an exter-
nal linear regulator.
The MAX1980 has a separate analog PWM supply volt-
age input (V
The battery input (V+) and 5V bias inputs (V
V
4.5V to 5.5V supply.
DD
IN
) can be tied together if the input source is a fixed
Driver Disable for Multiphase DC-DC Converter
<
η
V
OUT
CC
), the input currents of the overlapping
) and gate-driver supply input (V
5V Bias Supply (V
______________________________________________________________________________________
CC
) or falling edges (POL = GND)
Quick-PWM Slave Controller with
CC
CC
) causes the
and V
CC
DD
DD
and
).
)
The maximum current required from the 5V bias supply
to power V
power) is:
where I
frequency, and Q
sheets’ total gate-charge specification limits at
V
When DD is driven low, the MAX1980 disables the dri-
vers by forcing DL and DH low, effectively disabling the
slave controller. Disabling the MAX1980 for single-
phase operation allows the master controller to enter
low-power pulse-skipping operation under light load
conditions.
When DD is driven high, the MAX1980 enables the dri-
vers, allowing normal PWM operation (see the On-time
Control and Active Current Balancing section). Since
the slave controller cannot skip pulses, the master con-
troller should be configured for forced-PWM operation
while the MAX1980’s drivers are enabled. This PWM
control scheme forces the low-side gate drive wave-
form to be the complement of the high-side gate drive
waveform, allowing the inductor current to reverse.
During negative load and downward output-voltage
transitions, forced-PWM operation allows the converter
to sink current, rapidly pulling down the output voltage.
Another benefit of forced-PWM operation, the switching
frequency remains relatively constant over the full load
and input voltage ranges.
The MAX1980 slave controller enters a low-power
standby mode when the ILIM voltage (V
below 250mV (Table 4). Standby forces DL and DH
low, and disables the PWM controller to inhibit switch-
ing; however, the bias and fault-protection circuitry
remain active so the MAX1980 can continuously moni-
tor the ILIM input. When V
the PWM controller is enabled.
Table 3. Approximate K-Factor Errors
CONNECTION
I
GS
BIAS
= 5V.
Float
GND
TON
V
= I
CC
CC
CC
CC
is 525µA typical, f
+ f
(PWM controller) and V
SW
FREQUENCY
SETTING
(Q
G1
(kHz)
200
300
550
G1
and Q
+ Q
ILIM
G2
G2
K-FACTOR
) = 10mA to 45mA (typ)
is driven above 250mV,
are the MOSFET data
(µs)
3.3
1.8
SW
5
Standby Mode
Driver Disable
is the switching
DD
K-FACTOR
ILIM
(gate-drive
ERROR
MAX
(%)
10
10
10
) drops
15