Maxim MAX16904RAUE /V+ 2.1mhz, high-voltage, 600ma mini-buck converter Datasheet

19-5481; Rev 5; 6/12
KIT
ATION
EVALU
LE
B
A
IL
A
AV
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
Features
The MAX16904 is a small, synchronous buck converter
with integrated high-side and low-side switches. The
device is designed to deliver 600mA with input voltages
from +3.5V to +28V while using only 25µA quiescent
current at no load. Voltage quality can be monitored by
observing the PGOOD signal. The MAX16904 can operate in dropout by running at 97% duty cycle, making it
ideal for automotive and industrial applications.
The MAX16904 operates at a 2.1MHz frequency, allowing for small external components and reduced output
ripple. It guarantees no AM band interference. SYNC
input programmability enables three frequency modes
for optimized performance: forced fixed-frequency
operation, SKIP mode (ultra-low quiescent current of
25µA), and synchronization to an external clock. The
MAX16904 can be ordered with spread-spectrum frequency modulation, designed to minimize EMI-radiated
emissions due to the modulation frequency.
o Wide +3.5V to +28V Input Voltage Range
o Tolerates Input Voltage Transients to +42V
o 600mA Minimum Output Current with Overcurrent
Protection
o Fixed Output Voltages (+3.3V and +5V)
o 2.1MHz Switching Frequency with Three Modes of
Operation
25µA Ultra-Low Quiescent Current SKIP Mode
Forced Fixed-Frequency Operation
External Frequency Synchronization
o Optional Spread-Spectrum Frequency Modulation
o Power-Good Output
o Enable-Pin Compatible from +3.3V Logic Level to
+42V
o Thermal Shutdown Protection
o -40°C to +125°C Automotive Temperature Range
o 10-Pin TDFN-EP or 16-Pin TSSOP-EP Packages
The MAX16904 is available in a thermally enhanced,
3mm x 3mm, 10-pin TDFN package or a 16-pin TSSOP
package. The MAX16904 operates over the -40°C to
+125°C automotive temperature range.
o AEC-Q100 Qualified
Ordering Information
Applications
Automotive
Industrial
Military
PART
SPREAD
TEMP PINSPECTRUM RANGE PACKAGE
MAX16904RATB__/V+
Disabled
-40°C to
10 TDFN-EP*
+125°C
MAX16904RAUE__/V+
Disabled
-40°C to
16 TSSOP-EP*
+125°C
MAX16904SATB__/V+
Enabled
-40°C to
10 TDFN-EP*
+125°C
MAX16904SAUE__/V+
Enabled
-40°C to
16 TSSOP-EP*
+125°C
High-Voltage Input-Power DC-DC Applications
Note: Insert the desired suffix letters (from Selector Guide) into
the blanks to indicate the output voltage. Alternative output voltages available upon request.
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
*EP = Exposed pad.
Selector Guide appears at end of data sheet.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX16904
General Description
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
MAX16904
Typical Operating Circuits
33kΩ
SUP
4.7µF
VBAT LEVEL
SIGNAL
EN
*
MAX16904_50/V+
SYNC
BST
GND
0.1µF
4.7µH
5V AT 600mA
PGOOD
LX
10µF
20kΩ
PGND
BIAS
OUTS
2.2µF
33kΩ
SUP
4.7µF
VBAT LEVEL
SIGNAL
EN
*
MAX16904_33/V+
SYNC
BST
GND
0.1µF
3.3µH
3.3V AT 600mA
LX
PGOOD
10µF
20kΩ
PGND
OUTS
BIAS
2.2µF
*PLACE INPUT SUPPLY CAPACITORS AS CLOSE AS POSSIBLE TO THE SUP PIN. SEE THE APPLICATIONS INFORMATION SECTION FOR MORE DETAILS.
2
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
(Voltages referenced to GND.)
SUP, EN..................................................................-0.3V to +42V
BST to LX..................................................................-0.3V to +6V
LX..............................................................-0.3V to (VSUP + 0.3V)
BST .........................................................................-0.3V to +47V
OUTS ......................................................................-0.3V to +12V
SYNC, PGOOD, BIAS............................................-0.3V to +6.0V
PGND to GND .......................................................-0.3V to +0.3V
LX Continuous RMS Current .................................................1.0A
OUTS Short-Circuit Duration ......................................Continuous
ESD Protection
Human Body Model .........................................................±2kV
Machine Model ..............................................................±200V
Continuous Power Dissipation (TA = +70°C)
TDFN (derate 24.4 mW/°C above +70°C)......................1951mW
TSSOP (derate 26.1 mW/°C above +70°C) ...................2089mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TDFN
Junction-to-Ambient Thermal Resistance (θJA) ...........41°C/W
Junction-to-Case Thermal Resistance (θJC) ..................9°C/W
TSSOP
Junction-to-Ambient Thermal Resistance (θJA) ........38.3°C/W
Junction-to-Case Thermal Resistance (θJC) ..................3°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(VSUP = +14V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
VSUP
I SUP
CONDITIONS
(Note 2)
MIN
3.5
42
EN = low
4
8
EN = high, no load
25
35
VUVLO
Bias rising
VUVLO,HYS
Hysteresis
Bias Voltage
VBIAS
Bias Current Limit
IBIAS
MAX
28
t < 1s
EN = high, continuous, no switching
UV Lockout
TYP
1
2.8
3
V
µA
mA
3.2
0.4
+5.5V VSUP +42V
UNITS
5
V
V
10
mA
BUCK CONVERTER
VOUT = 5V, fixed frequency
VOUT,5V
Voltage Accuracy
VOUT = 5V, SKIP mode
(Note 3)
VOUT = 3.3V, fixed frequency
VOUT,3.3V
VOUT = 3.3V, SKIP mode
(Note 3)
6V VSUP 18V,
ILOAD = 0 to 600mA,
TA = -40°C to
+125°C
-2.0%
5
+2.5%
-2.0%
5
+4%
-2.0%
3.3
+2.5%
-2.0%
3.3
+4%
V
3
MAX16904
ABSOLUTE MAXIMUM RATINGS
MAX16904
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
ELECTRICAL CHARACTERISTICS (continued)
(VSUP = +14V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
SKIP-Mode Peak Current
I SKIP
High-Side DMOS RDSON
R ON,HS
Low-Side DMOS RDSON
R ON,LS
DMOS Peak Current-Limit
Threshold
Soft-Start Ramp Time
LX Rise Time
TYP
MAX
350
VBIAS = 5V
UNITS
mA
400
800
m
250
450
m
0.85
1.05
1.22
A
t SS
7
8
9
ms
tRISE,LX
t ON
PWM Switching Frequency
f SW
Spread-Spectrum Range
MIN
IMAX
Minimum On-Time
SYNC Input Frequency Range
CONDITIONS
5
80
Internally generated
f SYNC
SS
ns
1.925
2.1
1.8
Spread-spectrum option only
+6
VTHR,PGD
VOUT rising
93
VTHF,PGD
VOUT falling
ns
2.275
MHz
2.6
MHz
%
PGOOD
PGOOD Threshold
PGOOD Debounce
88
tDEB
91
94
10
%
µs
PGOOD High Leakage Current
ILEAK,PGD
TA = +25°C
1
µA
PGOOD Output Low Level
VOUT,PGD
Sinking 1mA
0.4
V
LOGIC LEVELS
EN Level
EN Input Current
SYNC Switching Threshold
SYNC Internal Pulldown
VIH,EN
2.4
0.6
VIL,EN
I IN,EN
VEN = V SUP = +42V, TA = +25°C
VIH,SYNC
1
1.4
0.4
VIL,SYNC
V
µA
V
RPD,SYNC
200
k
T SHDN
175
°C
T SHDN,HYS
15
°C
THERMAL PROTECTION
Thermal Shutdown
Thermal Shutdown Hysteresis
Note 2: When the typical minimum on-time of 80ns is violated, the device skips pulses.
Note 3: Guaranteed by design; not production tested.
4
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE (SKIP MODE)
5V, FFF MODE
3.3V, FFF MODE
40
30
20
40
5V PART
30
20
3.3V PART
10
10
0
0.2
0.3
0.4
0
0.6
0.5
2
1
0
-1
-2
-3
6
8 10 12 14 16 18 20 22 24 26 28
LOAD CURRENT (A)
6
8 10 12 14 16 18 20 22 24 26 28
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE
LOAD REGULATION
4
3
SKIP MODE
2
1
0
FFF MODE
-1
15
12
SUPPLY CURRENT (µA)
0.1
3
-4
MAX16904 toc04
0
4
-2
MAX16904 toc05
50
50
SUPPLY CURRENT (µA)
70
OUTPUT-VOLTAGE CHANGE (%)
EFFICIENCY (%)
80
60
60
MAX16904 toc03
3.3V, SKIP MODE
MAX16904 toc02
5V, SKIP MODE
90
MAX16904 toc01
100
LINE REGULATION
(ILOAD = 600mA)
OUTPUT VOLTAGE CHANGE (%)
EFFICIENCY vs. LOAD CURRENT
9
6
3
-3
0
-4
0
0.1
0.2
0.3
0.4
0.5
6
0.6
STARTUP RESPONSE
(ILOAD = 600mA)
1ms/div
8 10 12 14 16 18 20 22 24 26 28
INPUT VOLTAGE (V)
LOAD CURRENT (A)
SHUTDOWN WAVEFORM (ILOAD = 600mA)
MAX16904 toc06
MAX16904 toc07
VEN
5V/div
EN
5V/div
IL
1A/div
IINDUCTOR
0.5A/div
VOUT
5V/div
PGOOD
5V/div
VPGOOD
5V/div
VOUT
5V/div
20µs/div
5
MAX16904
Typical Operating Characteristics
(VSUP = +14V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VSUP = +14V, TA = +25°C, unless otherwise noted.)
LOAD TRANSIENT RESPONSE
(3.3V, SKIP MODE)
LOAD TRANSIENT RESPONSE
(3.3V, FIXED MODE)
MAX16904 toc09
MAX16904 toc08
600mA
IL
500mA/div
100mA
600mA
IL
500mA/div
100mA
VOUT
50mV/div
AC-COUPLED
5V
VBIAS
5V/div
VOUT
50mV/div
AC-COUPLED
5V
VBIAS
5V/div
5V
VPGOOD
5V/div
5V
VPGOOD
5V/div
40µs/div
40µs/div
LOAD TRANSIENT RESPONSE
(5V, SKIP MODE)
LOAD TRANSIENT RESPONSE
(5V, FIXED MODE)
MAX16904 toc11
MAX16904 toc10
600mA
IL
500mA/div
100mA
600mA
IL
500mA/div
100mA
VOUT
50mV/div
AC-COUPLED
VOUT
50mV/div
AC-COUPLED
5V
VBIAS
5V/div
5V
VBIAS
5V/div
5V
VPGOOD
5V/div
5V
VPGOOD
5V/div
40µs/div
40µs/div
UNDERVOLTAGE PULSE
(COLD CRANK)
STANDBY CURRENT
vs. LOAD CURRENT
MAX16904 toc12
MAX16904 toc13
500
450
VSUP
10V/div
400
350
VOUT
5V/div
VPGOOD
5V/div
IIN (µA)
MAX16904
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
300
250
200
150
100
ILOAD
500mA/div
50
0
10ms/div
0.01
0.1
ILOAD (mA)
6
1
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
TOP VIEW
BST
1
SUP
2
LX
3
PGND
4
OUTS
5
+
MAX16904
EP
10
EN
9
GND
8
BIAS
7
SYNC
6
PGOOD
TDFN
+
BST
1
16 N.C.
SUP
2
15 EN
SUP
3
14 GND
LX
4
LX
5
12 SYNC
PGND
6
11 PGOOD
PGND
7
OUTS
8
MAX16904
13 BIAS
10 N.C.
EP
9
N.C.
TSSOP
Pin Description
PIN
TDFN-EP
TSSOP-EP
1
1
NAME
FUNCTION
BST
Bootstrap Capacitor for High-Side Driver (0.1µF)
Voltage Supply Input. Connect a 4.7µF ceramic capacitor from SUP to PGND. Place the
capacitor very close to the SUP pin. For the TSSOP-EP package, connect both SUP pins
together for proper operation.
2
2, 3
SUP
3
4, 5
LX
4
6, 7
PGND
Power Ground. For the TSSOP-EP package, connect both PGND pins together for proper
operation.
5
8
OUTS
Buck Regulator Voltage-Sense Input. Bypass OUTS to PGND with a 10µF or larger X7R
ceramic capacitor.
6
11
PGOOD
7
12
SYNC
8
13
BIAS
+5V Internal Logic Supply. Connect a 2.2µF ceramic capacitor from BIAS to GND.
9
14
GND
Analog Ground
10
15
EN
9, 10, 16
N.C.
EP
Buck Switching Node. LX is high impedance when the device is off. For the TSSOP
package, connect both LX pins together for proper operation.
Open-Drain Power-Good Output. External pullup resistor required for automatic SKIP
mode operation.
Sync Input. SYNC allows the device to synchronize to other supplies. When connected
to GND or unconnected, SKIP mode is enabled under light loads. When connected to a
clock source or BIAS, forced PWM mode is enabled.
Enable Input. EN is high-voltage compatible. Drive EN HIGH for normal operation.
No Connection. Not internally connected.
Exposed Pad. Connect EP to PGND. Do not use EP as the only ground connection.
7
MAX16904
Pin Configurations
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
MAX16904
Functional Diagram
SYNC
REF
EN
HVLDO
BANDGAP
OSC
BST
BIAS
SUP
CLK
HSD
SOFT-START
CURRENT-SENSE
AND
SLOPE COMPENSATION
LOGIC
CONTROL
LX
BIAS
OUTS
PWM
LSD
EAMP
COMP
VGOOD
MAX16904
PGND
PGOOD
8
GND
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
The MAX16904 is a small, current-mode buck converter
that features synchronous rectification and requires no
external compensation network. The device is designed
for 600mA output current, and can stay in dropout by
running at 97% duty cycle. It provides an accurate output voltage within the +6.5V to +18V input range.
Voltage quality can be monitored by observing the
PGOOD signal. The device operates at 2.1MHz (typ)
frequency, which allows for small external components,
reduced output ripple, and guarantees no AM band
interference.
The device features an ultra-low 25µA (typ) quiescent
supply current in standby mode. Standby mode is
entered when load currents are below 5mA and when
SYNC is low. The device operates from a +3.5V to
+28V supply voltage and tolerates transients up to
+42V, making it ideal for automotive applications. The
device is available in factory-trimmed output voltages
from 1.8V to 10.7V in 100mV steps. Contact the factory
for availability of voltage options.
Enable (EN)
The device is activated by driving EN high. EN is compatible from a +3.3V logic level to automotive battery
levels. EN can be controlled by microcontrollers and
automotive KEY or CAN inhibit signals. The EN input
has no internal pullup/pulldown current to minimize
overall quiescent supply current. To realize a programmable undervoltage lockout level, use a resistordivider from SUP to EN to GND.
BIAS/UVLO
The device features undervoltage lockout. When the
device is enabled, an internal bias generator turns on.
LX begins switching after VBIAS has exceeded the internal undervoltage lockout level VUVLO = 3V (typ).
Soft-Start
The device features an internal soft-start timer. The output voltage soft-start ramp time is 8ms (typ). If a short
circuit or undervoltage is encountered, after the softstart timer has expired, the device is disabled for 30ms
(typ) and it reattempts soft-start again. This pattern
repeats until the short circuit has been removed.
Oscillator/Synchronization and
Efficiency (SYNC)
The device has an on-chip oscillator that provides a
switching frequency of 2.1MHz (typ). Depending on the
condition of SYNC, two operation modes exist. If SYNC
is unconnected or at GND, the device must operate in
highly efficient pulse-skipping mode if the load current
is below the SKIP mode current threshold. If SYNC is at
BIAS or has a frequency applied to it, the device is in
forced PWM mode. The device offers the best of both
worlds. The device can be switched during operation
between forced PWM mode and SKIP mode by switching SYNC.
SKIP Mode Operation
SKIP mode is entered when the SYNC pin is connected
to ground or is unconnected and the peak load current
is < 350mA (typ). In this mode, the high-side FET is
turned on until the current in the inductor is ramped up
to 350mA (typ) peak value and the internal feedback
voltage is above the regulation voltage (1.2V typ). At
this point, both the high-side and low-side FETs are
turned off. Depending on the choice of the output
capacitor and the load current the high-side FET turns
on when OUTS (valley) drops below the 1.2V (typ) feedback voltage.
Achieving High Efficiency at Light Loads
The device operates with very low quiescent current at
light loads to enhance efficiency and conserve battery
life. When the device enters SKIP mode the output current is monitored to adjust the quiescent current.
When the output current is < 5mA, the device operates in
the lowest quiescent current mode also called the standby mode. In this mode, the majority of the internal circuitry (excluding that necessary to maintain regulation) in the
device, including the internal high-voltage LDO, is turned
off to save current. Under no load and with SKIP mode
enabled, the device draws only 25µA (typ) current. For
load currents > 5mA, the device enters normal SKIP
mode while still maintaining very high efficiency.
Controlled EMI with Forced-Fixed Frequency
In forced PWM mode, the device attempts to operate at
a constant switching frequency for all load currents. For
tightest frequency control, apply the operating frequency to SYNC. The advantage of this mode is a constant
switching frequency, which improves EMI performance;
the disadvantage is that considerable current can be
thrown away. If the load current during a switching
cycle is less than the current flowing through the inductor, the excess current is diverted to GND. With no
external load present, the operating current is in the
10mA range.
Extended Input Voltage Range
In some cases, the device is forced to deviate from its
operating frequency independent of the state of SYNC.
For input voltages above 18V, the required duty cycle
to regulate its output may be smaller than the minimum
on-time (80ns, typ). In this event, the device is forced to
lower its switching frequency by skipping pulses.
9
MAX16904
Detailed Description
MAX16904
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
If the input voltage is reduced and the device
approaches dropout, it tries to turn on the high-side
FET continuously. To maintain gate charge on the highside FET, the BST capacitor must be periodically
recharged. To ensure proper charge on the BST
capacitor when in dropout, the high-side FET is turned
off every 6.5µs and the low-side FET is turned on for
about 150ns. This gives an effective duty cycle
of > 97% and a switching frequency of 150kHz when in
dropout.
Spread-Spectrum Option
The device has an optional spread-spectrum version. If
this option is selected, then the internal operating frequency varies by +6% relative to the internally generated operating frequency of 2.1MHz (typ). Spread
spectrum is offered to improve EMI performance of the
device. By varying the frequency 6% only in the positive direction, the device still guarantees that the
2.1MHz frequency does not drop into the AM band limit
of 1.8MHz. Additionally, with the low minimum on-time
of 80ns (typ) no pulse skipping is observed for a 5V
output with 18V input maximum battery voltage in
steady state.
The internal spread spectrum does not interfere with
the external clock applied on the SYNC pin. It is active
only when the device is running with internally generated switching frequency.
Power-Good (PGOOD)
The device features an open-drain power-good output.
PGOOD is an active-high output that pulls low when the
output voltage is below 91% of its nominal value.
PGOOD is high impedance when the output voltage is
above 93% of its nominal value. Connect a 20kΩ (typ)
pullup resistor to an external supply or the on-chip BIAS
output.
Overcurrent Protection
The device limits the peak output current to 1.05A (typ).
To protect against short-circuit events, the device shuts
off when OUTS is below 1.5V (typ) and one overcurrent
event is detected. The device attempts a soft-start
restart every 30ms and stays off if the short circuit has
not been removed. When the current limit is no longer
present, it reaches the output voltage by following the
normal soft-start sequence. If the device die reaches
the thermal limit of +175°C (typ) during the current-limit
event, it immediately shuts off.
Thermal-Overload Protection
The device features thermal-overload protection. The
device turns off when the junction temperature exceeds
10
+175°C (typ). Once the device cools by 15°C (typ), it
turns back on with a soft-start sequence.
Applications Information
Inductor Selection
Three key inductor parameters must be specified for
operation with the device: inductance value (L), peak
inductor current (IPEAK), and inductor saturation current
(ISAT). The minimum required inductance is a function
of operating frequency, input-to-output voltage differential, and the peak-to-peak inductor current
(∆IP-P). Higher ∆IP-P allows for a lower inductor value,
while a lower ∆IP-P requires a higher inductor value. A
lower inductor value minimizes size and cost, improves
large-signal and transient response, but reduces efficiency due to higher peak currents and higher peak-topeak output-voltage ripple for the same output
capacitor. On the other hand, higher inductance
increases efficiency by reducing the ripple current.
Resistive losses due to extra wire turns can exceed the
benefit gained from lower ripple current levels especially when the inductance is increased without also allowing for larger inductor dimensions. A good compromise
is to choose ∆IP-P equal to 30% of the full load current.
Use the following equation to calculate the inductance:
L=
VOUT (VIN − VOUT )
VIN × fSW × ∆IP − P
VIN and VOUT are typical values so that efficiency is
optimum for typical conditions. The switching frequency
is ~2.1MHz. The peak-to-peak inductor current, which
reflects the peak-to-peak output ripple, is worse at the
maximum input voltage. See the Output Capacitor section to verify that the worst-case output ripple is acceptable. The inductor saturation current is also important to
avoid runaway current during continuous output short
circuit. The output current may reach 1.22A since this is
the maximum current limit. Choose an inductor with a
saturation current of greater than 1.22A to ensure proper operation and avoid runaway.
Input Capacitor
The discontinuous input current of the buck converter
causes large input ripple current. The switching frequency, peak inductor current, and the allowable peak-topeak input-voltage ripple dictate the input capacitance
requirement. Increasing the switching frequency or the
inductor value lowers the peak-to-average current ratio
yielding a lower input capacitance requirement.
The input ripple comprises mainly of ∆VQ (caused by
the capacitor discharge) and ∆VESR (caused by the
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
I
× D(1 − D)
CIN = OUT
∆VQ × fSW
where:
∆IP − P =
(VIN − VOUT ) × VOUT
VIN × fSW × L
and:
V
D = OUT
VIN
where IOUT is the output current, D is the duty cycle,
and f SW is the switching frequency. Use additional
input capacitance at lower input voltages to avoid possible undershoot below the UVLO threshold during transient loading.
Output Capacitor
The allowable output-voltage ripple and the maximum
deviation of the output voltage during step load currents determine the output capacitance and its ESR.
The output ripple comprises of ∆VQ (caused by the
capacitor discharge) and ∆VESR (caused by the ESR of
the output capacitor). Use low-ESR ceramic or aluminum electrolytic capacitors at the output. For aluminum electrolytic capacitors, the entire output ripple is
contributed by ∆VESR. Use the ESROUT equation to calculate the ESR requirement and choose the capacitor
accordingly. If using ceramic capacitors, assume the
contribution to the output ripple voltage from the ESR
and the capacitor discharge to be equal. The following
equations show the output capacitance and ESR
requirement for a specified output-voltage ripple.
ESR =
COUT =
∆VESR
∆IP − P
∆IP − P
8 × ∆VQ × fSW
where:
∆IP − P =
(VIN − VOUT ) × VOUT
VIN × fSW × L
VOUT _ RIPPLE ≅ ∆VESR + ∆VQ
∆IP-P is the peak-to-peak inductor current as calculated
above and fSW is the converter’s switching frequency.
The allowable deviation of the output voltage during
fast transient loads also determines the output capacitance and its ESR. The output capacitor supplies the
step load current until the converter responds with a
greater duty cycle. The response time (t RESPONSE )
depends on the closed-loop bandwidth of the converter. The device’s high switching frequency allows for a
higher closed-loop bandwidth, thus reducing
tRESPONSE and the output capacitance requirement.
The resistive drop across the output capacitor’s ESR
and the capacitor discharge causes a voltage droop
during a step load. Use a combination of low-ESR tantalum and ceramic capacitors for better transient load
and ripple/noise performance. Keep the maximum output-voltage deviations below the tolerable limits of the
electronics being powered. When using a ceramic
capacitor, assume an 80% and 20% contribution from
the output capacitance discharge and the ESR drop,
respectively. Use the following equations to calculate
the required ESR and capacitance value:
ESROUT =
∆VESR
ISTEP
I
× tRESPONSE
COUT = STEP
∆VQ
where I STEP is the load step and t RESPONSE is the
response time of the converter. The converter response
time depends on the control-loop bandwidth.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
power losses and clean stable operation. Use a multilayer
board wherever possible for better noise immunity. Refer
to the MAX16904 Evaluation Kit for recommended PCB
layout. Follow these guidelines for a good PCB layout:
1) The input capacitor (4.7µF, see the applications
schematic in the Typical Operating Circuits) should be
placed right next to the SUP pins (pins 2 and 3 on the
TSSOP-EP package). Because the device operates at
2.1MHz switching frequency, this placement is critical
for effective decoupling of high-frequency noise from
the SUP pins.
11
MAX16904
ESR of the input capacitor). The total voltage ripple is
the sum of ∆VQ and ∆VESR. Assume the input-voltage
ripple from the ESR and the capacitor discharge is
equal to 50% each. The following equations show the
ESR and capacitor requirement for a target voltage ripple at the input:
∆VESR
ESR =
∆IP − P ⎞
⎛
⎜⎝ IOUT +
⎟
2 ⎠
MAX16904
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
2) Solder the exposed pad to a large copper plane
area under the device. To effectively use this copper
area as heat exchanger between the PCB and ambient, expose the copper area on the top and bottom
side. Add a few small vias or one large via on the
copper pad for efficient heat transfer. Connect the
exposed pad to PGND ideally at the return terminal
of the output capacitor.
3) Isolate the power components and high current
paths from sensitive analog circuitry.
4) Keep the high current paths short, especially at the
ground terminals. The practice is essential for stable
jitter-free operation.
5) Connect the PGND and GND together preferably at
the return terminal of the output capacitor. Do not
connect them anywhere else.
1MΩ
CHARGE-CURRENTLIMIT RESISTOR
HIGHVOLTAGE
DC
SOURCE
CS
100pF
ESD Protection
The device’s ESD tolerance is rated for Human Body
Model and Machine Model. The Human Body Model
discharge components are CS = 100pF and RD = 1.5kΩ
(Figure 1). The Machine Model discharge components
are CS = 200pF and RD = 0Ω (Figure 2).
RD
1.5kΩ
RD
0Ω
CHARGE-CURRENTLIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Figure 1. Human Body ESD Test Circuit
12
6) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCB to enhance full load efficiency and
power dissipation capability.
7) Route high-speed switching nodes away from sensitive analog areas. Use internal PCB layers as PGND
to act as EMI shields to keep radiated noise away
from the device and analog bypass capacitor.
DEVICE
UNDER
TEST
HIGHVOLTAGE
DC
SOURCE
CS
200pF
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Figure 2. Machine Model ESD Test Circuit
DEVICE
UNDER
TEST
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
OUTPUT VOLTAGE
(V)
PIN-PACKAGE
SPREAD-SPECTRUM
SWITCHING FREQUENCY
TOP
MARK
MAX16904RATB50+
5.0
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
⎯
AYG
MAX16904RATB50/V+
5.0
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
⎯
AVY
MAX16904RAUE50/V+
5.0
16 TSSOP-EP*
(5mm x 4.4mm)
⎯
⎯
MAX16904SATB50/V+
5.0
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AWA
MAX16904SATB51/V+†
5.1
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AYX
MAX16904SATB52/V+†
5.2
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AYY
MAX16904SAUE50/V+
5.0
16 TSSOP-EP*
(5mm x 4.4mm)
Yes
⎯
MAX16904RATB33/V+
3.3
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
⎯
AVX
MAX16904RAUE33/V+
3.3
16 TSSOP-EP*
(5mm x 4.4mm)
⎯
⎯
MAX16904SATB33/V+
3.3
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AVZ
MAX16904SAUE33/V+
3.3
16 TSSOP-EP*
(5mm x 4.4mm)
Yes
⎯
MAX16904RAUE18/V+†
1.8
16 TSSOP-EP*
(5mm x 4.4mm)
⎯
⎯
MAX16904SATB60/V+†
6.0
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AYO
MAX16904SATB80/V+†
8.0
10 TDFN-EP*
(3mm x 3mm x 0.75mm)
Yes
AYN
PART
Note: All devices operate over the -40°C to +125°C automotive temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V denotes an automotive qualified part.
*EP = Exposed pad.
†Future product–contact factory for availability.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 TDFN-EP
T1033+1
21-0137
90-0003
16 TSSOP-EP
U16E+3
21-0108
90-0120
13
MAX16904
Selector Guide
MAX16904
2.1MHz, High-Voltage,
600mA Mini-Buck Converter
Revision History
REVISION
NUMBER
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
0
9/10
Initial release
—
1
11/10
Added new output voltage trim to Selector Guide
12
2
3/11
Updated the Voltage Accuracy and the DMOS Peak Current-Limit Threshold parameters
in the Electrical Characteristics, updated TOCs 1, 6, and 8–13
3
7/11
Added the MAX16904RATB50+ part number to the Selector Guide
13
4
3/12
Added new future part numbers to the Selector Guide
13
5
6/12
Updated Selector Guide to include MAX16904SATB51/V+ and the MAX16904SATB52/V+
13
3, 4, 5, 6
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
14
_______________Maxim Integrated Products, Inc. 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2012 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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