MAX17512ATP+ Maxim Integrated, MAX17512ATP+ Datasheet - Page 10

• Manufacturer Part Number: MAX17512ATP+
• Description: Current & Power Monitors & Regulators High Speed Valley Current Regulator
• Manufacturer: Maxim Integrated

Specifications of MAX17512ATP+

• Product: Current Regulators
• Supply Voltage - Max: 18 V
• Supply Voltage - Min: 6.5 V
• Input Voltage Range: 6.5 V to 18 V

The device employs a modified constant on-time valley
current-control scheme to generate the programmed
inductor current and inductor ripple current. The heart of
this control scheme is the one-shot that sets the high-side
switch on-time. This fast, low-jitter, adjustable one-shot
includes circuitry that varies the on-time in response to
the resistance value connected at the RTON pin. In this
time period, the inductor current rises with a slope equal
to the ratio of input voltage to the inductance. The control
scheme turns off the high-side MOSFET and turns on
the low-side MOSFET after the programmed on-time.
The low-side MOSFET turns on until the inductor valley
current falls below the programmed threshold at the
ICMD pin, as determined by the low-side current-sense
comparator. A time period that comprises the high-side
MOSFET on-time and low-side MOSFET on-time is called
a switching time period. The low-side current-sense
comparator has very low hysteresis and low propaga-
tion delay. The overall current-sense comparator delay
is 20ns (typ). This feature is useful in high-performance
applications such as envelope tracking in base stations.
The device incorporates a comparator that monitors the
change in current-command voltage from the previously
programmed command value. If the change in current-
command voltage is greater than 70mV (typ), then the
comparator ensures that the high-side MOSFET is on
until the inductor current is close to the latest current
command. This innovative scheme ensures a hysteretic
type of behaviour for step changes in the current com-
mand, as shown in
Figure 1. Modified Constant On-Time Valley Current-Control
Scheme
V
ICMD
V
I
LX_
LX_
High-Speed, Constant On-Time, Valley Current
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Figure
1.
Control Scheme
Regulator for Tracking Applications
The device provides a FLT signal that serves as a power-
OK signal to the system. FLT is an open-drain signal and
requires a pullup resistor to the preferred supply voltage.
The FLT signal monitors the input voltage (PVIN), AVCC
and die temperature, and pulls high when all these inputs
are within their respective operating regions. The FLT
signal pulls low when either of the inputs fall below its
falling threshold.
The device contains an internal thermal sensor that limits
the total power dissipation to protect it in the event of an
extended thermal-fault condition. When the die tempera-
ture exceeds +160NC, the thermal sensor shuts down the
device, turning it off to allow the die to cool. After the die
temperature falls by 20NC (typ), the device restarts.
AVCC supplies all the control circuitry in the device, and
similarly, PVCC supplies the internal MOSFET gate-driver
circuitry. Both AVCC and PVCC require a 5V power sup-
ply for the internal blocks to operate. For this purpose,
the device integrates a linear regulator that generates
a 5V supply (V
connected to AVCC through a lowpass filter, as shown in
Figure
Figure 2. Configuring V
2. PVCC can be connected directly to V
C
R
CC
V
CC
Applications Information
). The internal linear regulator can be
AVCC
Configuring AVCC and PVCC
CC
V
CC
to Power Control and Drive Circuitry
V
CC
MAX17512
FLT Power-OK Signal
LDO
MAX17512
Thermal Shutdown
AVIN
PVCC
CC
.