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PDF MAX16936 Data sheet ( Hoja de datos )
| Número de pieza | MAX16936 | |
| Descripción | Step-Down Converter | |
| Fabricantes | Maxim Integrated | |
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MAX16936
36V, 220kHz to 2.2MHz Step-Down Converter
with 28µA Quiescent Current
General Description
The MAX16936 is a 2.5A current-mode step-down con-
verter with integrated high-side and low-side MOSFETs
designed to operate with an external Schottky diode
for better efficiency. The low-side MOSFET enables
fixed-frequency forced-PWM (FPWM) operation under
light-load applications. The device operates with input
voltages from 3.5V to 36V, while using only 28FA qui-
escent current at no load. The switching frequency is
resistor programmable from 220kHz to 2.2MHz and can
be synchronized to an external clock. The MAX16936’s
output voltage is available as 5V/3.3V fixed or adjustable
from 1V to 10V. The wide input voltage range along with its
ability to operate at 98% duty cycle during undervoltage
transients make the MAX16936 ideal for automotive and
industrial applications.
Under light-load applications, the FSYNC logic input
allows the MAX16936 to either operate in skip mode for
reduced current consumption or fixed-frequency FPWM
mode to eliminate frequency variation to minimize EMI.
Fixed-frequency FPWM mode is extremely useful for
power supplies designed for RF transceivers where tight
emission control is necessary. Protection features include
cycle-by-cycle current limit and thermal shutdown with
automatic recovery. Additional features include a power-
good monitor to ease power-supply sequencing and a
180N out-of-phase clock output relative to the internal
oscillator at SYNCOUT to create cascaded power sup-
plies with multiple MAX16936s.
The MAX16936 operates over the -40NC to +125NC
automotive temperature range and is available in 16-pin
TSSOP-EP and 5mm x 5mm, 16-pin TQFN-EP packages.
Features
S Wide 3.5V to 36V Input Voltage Range
S 42V Load Dump Protection
S Enhanced Current-Mode Control Architecture
S Fixed Output Voltage with ±2% Accuracy (5V/3.3V)
or Externally Resistor Adjustable (1V to 10V)
S 220kHz to 2.2MHz Switching Frequency with Three
Operation Modes
28µA Ultra-Low Quiescent Current Skip Mode
Forced Fixed-Frequency Operation
External Frequency Synchronization
S Spread-Spectrum Frequency Modulation
S Automatic LX Slew Rate Adjustment for Optimum
Efficiency Across Operating Frequency Range
S 180° Out-of-Phase Clock Output at SYNCOUT
S Low-BOM-Count Current-Mode Control
Architecture
S Power-Good Output
S Enable Input Compatible from 3.3V Logic Level
to 42V
S Thermal Shutdown Protection
S -40°C to +125°C Automotive Temperature Range
S AEC-Q100 Qualified
Applications
Point of Load Applications
Distributed DC Power Systems
Navigation and Radio Head Units
Ordering Information/Selector Guide appears at end of data
sheet.
Typical Application Circuit appears at end of data sheet.
For related parts and recommended products to use with this part, refer to: www.maximintegrated.com/MAX16936.related
For pricing, delivery, and ordering information, please contact Maxim Direct at
1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
19-6626; Rev 1; 4/13
Free Datasheet http://www.datasheet4u.com/
1 page  
MAX16936
36V, 220kHz to 2.2MHz Step-Down Converter
with 28µA Quiescent Current
Typical Operating Characteristics
(VSUP = VSUPSW = 14V, VEN = 14V, VOUT = 5V, VFYSNC = 0V, RFOSC = 12kI, TA = +25NC, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
100
90 fSW = 2.2MHz, VIN = 14V
5V SKIP MODE
80
70
60 3.3V
50 3.3V 5V
40
PWM MODE
30
20
10
0
0
0.001
0.1
LOAD CURRENT (A)
10
EFFICIENCY vs. LOAD CURRENT
100
90
fSW = 400kHz, VIN = 14V
SKIP MODE
80
5V
70 5V
60
3.3V
50
3.3V
PWM MODE
40
30
20
10
0
0
0.001
0.1
LOAD CURRENT (A)
10
VOUT LOAD REGULATION
5.10
5.08
VOUT = 5V, VIN = 14V
SKIP MODE
5.06
5.04 400kHz
5.02
5.00
4.98
4.96
2.2MHz
4.94
4.92
4.90
0
0.5 1.0 1.5 2.0
ILOAD (A)
2.5
VOUT LOAD REGULATION
5.10
5.08
VOUT = 5V, VIN = 14V
PWM MODE
5.06
5.04
400kHz
5.02
5.00
4.98
4.96
2.2MHz
4.94
4.92
4.90
0
0.5 1.0 1.5 2.0
ILOAD (A)
2.5
FSW vs. LOAD CURRENT
2.30
VIN = 14V,
2.28 PWM MODE
2.26
2.24 VOUT = 5V
2.22
2.20
2.18
2.16 VOUT = 3.3V
2.14
2.12
2.10
0
0.5 1.0 1.5 2.0
ILOAD (A)
2.5
FSW vs. LOAD CURRENT
435
VIN = 14V,
434 PWM MODE
433
432 VOUT = 5V
431
430
429
428 VOUT = 3.3V
427
426
425
0
0.5 1.0 1.5 2.0
ILOAD (A)
2.5
FSW vs. TEMPERATURE
2.28 VIN = 14V,
PWM MODE
2.24
2.20
VOUT = 5V
2.16
2.12
2.08
2.04
VOUT = 3.3V
2.00
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
SWITCHING FREQUENCY vs. RFOSC
2.50
2.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
12 42 72 102 132
RFOSC (kΩ)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
50
45
40
35
30
25
20
15 5V/2.2MHz
SKIP MODE
10
6 16
26
SUPPLY VOLTAGE (V)
36
Maxim Integrated
5
5 Page 
MAX16936
36V, 220kHz to 2.2MHz Step-Down Converter
with 28µA Quiescent Current
Spread-Spectrum Option
The MAX16936 has an internal spread-spectrum option
to optimize EMI performance. This is factory set and
the S-version of the IC should be ordered. For spread-
spectrum-enabled ICs, the operating frequency is varied
±6% centered on FOSC. The modulation signal is a trian-
gular wave with a period of 110µs at 2.2MHz. Therefore,
FOSC will ramp down 6% and back to 2.2MHz in 110µs
and also ramp up 6% and back to 2.2MHz in 110µs. The
cycle repeats.
For operations at FOSC values other than 2.2MHz, the
modulation signal scales proportionally, e.g., at 400kHz,
the 110µs modulation period increases to 110µs x
2.2MHz/400MHz = 550µs.
The internal spread spectrum is disabled if the IC is
synced to an external clock. However, the IC does not fil-
ter the input clock and passes any modulation (including
spread-spectrum) present on the driving external clock
to the SYNCOUT pin.
Automatic Slew-Rate Control on LX
The MAX16936 has automatic slew-rate adjustment
that optimizes the rise times on the internal HSFET gate
drive to minimize EMI. The IC detects the internal clock
frequency and adjusts the slew rate accordingly. When
the user selects the external frequency setting resistor
RFOSC such that the frequency is > 1.1MHz, the HSFET
is turned on in 4ns (typ). When the frequency is < 1.1MHz
the HSFET is turned on in 8ns (typ). This slew-rate control
optimizes the rise time on LX node externally to minimize
EMI while maintaining good efficiency.
Internal Oscillator (FOSC)
The switching frequency, fSW, is set by a resistor (RFOSC)
connected from FOSC to AGND. See Figure 3 to select the
correct RFOSC value for the desired switching frequency.
For example, a 400kHz switching frequency is set with
RFOSC = 732kI. Higher frequencies allow designs with
lower inductor values and less output capacitance.
Consequently, peak currents and I2R losses are lower
at higher switching frequencies, but core losses, gate
charge currents, and switching losses increase.
Synchronizing Output (SYNCOUT)
SYNCOUT is an open-drain output that outputs a 180N
out-of-phase signal relative to the internal oscillator.
Overtemperature Protection
Thermal-overload protection limits the total power dis-
sipation in the device. When the junction temperature
exceeds 175NC (typ), an internal thermal sensor shuts
Maxim Integrated
down the internal bias regulator and the step-down con-
troller, allowing the device to cool. The thermal sensor
turns on the device again after the junction temperature
cools by 15NC.
Applications Information
Setting the Output Voltage
Connect FB to BIAS for a fixed +5V/+3.3 output voltage.
To set the output to other voltages between 1V and 10V,
connect a resistive divider from output (OUT) to FB to
AGND (Figure 2). Use the following formula to determine
the RFB2 of the resistive divider network:
RFB2 = RTOTAL x VFB/VOUT
where VFB = 1V, RTOTAL = selected total resistance of
RFB1, RFB2 in ω, and VOUT is the desired output in volts.
Calculate RFB1 (OUT to FB resistor) with the following
equation:
=RFB1
RFB2
VOUT
VFB
−
1
where VFB = 1V (see the Electrical Characteristics table).
FPWM/Skip Modes
The MAX16936 offers a pin selectable skip mode or
fixed-frequency PWM mode option. The IC has an
internal LS MOSFET that turns on when the FSYNC pin
is connected to VBIAS or if there is a clock present on
the FSYNC pin. This enables the fixed-frequency-forced
PWM mode operation over the entire load range. This
option allows the user to maintain fixed frequency over
the entire load range in applications that require tight
control on EMI. Even though the MAX16936 has an inter-
nal LS MOSFET for fixed-frequency operation, an exter-
nal Schottky diode is still required to support the entire
load range. If the FSYNC pin is connected to GND, the
skip mode is enabled on the MAX16936.
MAX16936
FB
VOUT
RFB1
RFB2
Figure 2. Adjustable Output Voltage Setting
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX16936.PDF ] | |
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