MAX17007GTI+ Maxim Integrated Products, MAX17007GTI+ Datasheet - Page 22

• 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

When SKIP is pulled to GND, the MAX17007/MAX17008
remain in pulse-skipping mode. Since the output is not
able to sink current, the timing for negative dynamic out-
put-voltage transitions depends on the load current and
output capacitance. Letting the output voltage drift down
is typically recommended in order to reduce the potential
for audible noise since this eliminates the input current
surge during negative output-voltage transitions. Figure 5
shows the pulse-skipping/discontinuous crossover point.
Leaving SKIP unconnected or connecting SKIP to 3.3V
activates a unique pulse-skipping mode with a mini-
mum switching frequency of 25kHz. This ultrasonic
pulse-skipping mode eliminates audio-frequency mod-
ulation that would otherwise be present when a lightly
loaded controller automatically skips pulses. In ultra-
sonic mode, the controller automatically transitions to
fixed-frequency PWM operation when the load reaches
the same critical conduction point (I
occurs when normally pulse skipping.
An ultrasonic pulse occurs when the controller detects
that no switching has occurred within the last 30µs.
Once triggered, the ultrasonic controller pulls DL high,
turning on the low-side MOSFET to induce a negative
inductor current (Figure 6). After the inductor current
reaches the negative ultrasonic current threshold, the
controller turns off the low-side MOSFET (DL pulled
low) and triggers a constant on-time (DH driven high).
When the on-time has expired, the controller reenables
the low-side MOSFET until the controller detects that
the inductor current dropped below the zero-crossing
threshold. Starting with a DL pulse greatly reduces the
peak output voltage when compared to starting with a
DH pulse.
Dual and Combinable QPWM Graphics
Core Controllers for Notebook Computers
Figure 5. Pulse-Skipping/Discontinuous Crossover Point
22
______________________________________________________________________________________
0
∆I
∆t
ON-TIME
=
Ultrasonic Mode ( S S K K I I P P = Open = 3.3V)
V
IN
- V
L
OUT
TIME
LOAD(SKIP)
I
I
PEAK
LOAD
= I
PEAK
/2
) that
The output voltage at the beginning of the ultrasonic
pulse determines the negative ultrasonic current thresh-
old, resulting in the following equations for SMPS1:
where V
1.05V in preset mode, and R
resistance seen across CSH1 to CSL1.
Similarly for SMPS2:
where V
in preset mode, and R
tance seen across CSH2 to CSL2.
In combined mode, ultrasonic mode setting is disabled,
and the SKIP = OPEN (3.3V) setting is identical to the
SKIP = GND setting.
Figure 6. Ultrasonic Waveform
V
V
V
ISONIC
V
ISONIC
ISONIC
CSL2
CSL1
ISONIC
0
I
SONIC
1
> 0.7V in adjustable mode, V
1
2
> V
(SMPS1 adjustable mode)
2
(SMPS2 adjustable mode)
=
=
=
(SMPS1 preset mode)
=
(SMPS2 preset mode)
I R
I R
L
I R
REFIN1
L
L
40µs (MAX)
1
I R
1
L
2
2
CS
CS
CS
CS
1
1
CS2
2
=
2
=
in adjustable mode, V
=
(
=
V
(
1 05
(
is the current-sense resis-
REFIN
1 5
(
.
0 7
.
CS1
ZERO-CROSSING
DETECTION
.
V V
V V
ON-TIME (t
V V
1
−
−
−
is the current-sense
−
CSL
V
CSL
FB
CSL
ON
2
2
1
)
)
1
)
)
)
×
×
×
INDUCTOR
CURRENT
CSL2
×
0 65
0 65
0 65
.
0 65
.
.
.
CSL1
> 1.5V
>