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MAX16945TGUT#TG16
30mA Inverting Charge Pump in SOT23 for EMI-Sensitive Automotive Applications
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
General DescriptionThe MAX16945 ultra-small, monolithic, CMOS charge-
pump voltage inverter accepts an input voltage ranging
from +1.4V to +5.5V. This device features an ultra-low
12Ωoutput resistance, permitting loads of up to 30mA
at +105°C with maximum efficiency. The MAX16945
operates at a frequency of 125kHz, allowing use of
small external components. Its small external compo-
nents, micropower shutdown mode, and wide tempera-
ture range make this device ideal for both automotive
and industrial applications.
Oscillator control circuitry and four power MOSFET
switches are included on-chip. The MAX16945 comes
in a 6-pin SOT23 package and operates over -40°C
to +105°C.
ApplicationsAutomotive and Industrial Equipment
Small LCD Panels
Negative Supply from +5V or +3.3V Logic
Supplies
GaAsFET Bias Supplies
Handy-Terminals, PDAs
Features+1.4V to +5.5V Input Voltage Range30mA Guaranteed Output Current at +105°CSlew-Rate Limited to Reduce EMI0.1µA Logic-Controlled ShutdownLow 12ΩOutput ResistanceStartup Current Limited6-Pin SOT23 PackageAEC-Q100 QualifiedSHDN5
TOP VIEW
GNDC1-
C1+OUT
SOT236
MAX1694524
Pin ConfigurationC1+C1-
SHDN
OUT
GND
1µF
1µF
OFF
INPUT
1.5V TO 5.5V
NEGATIVE
OUTPUT
-1 ✕ VIN
60mA
MAX16945
Typical Operating Circuit#Denotes an RoHS-compliant device that may include lead that
is exempt under RoHS requirements.
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Note: The MAX16945 requires a special solder temperatureprofile described in the Absolute Maximum Ratings section.
Ordering Information
PARTTEMP RANGEPIN-PACKAGE MAX16945TGUT# -40°C to +105°C 6 SOT23
MAX16945TGUT/V+ -40°C to +105°C 6 SOT23
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, C1 = C2 =2.2µF, VIN= VSHDN= +5V, VGND= 0, TA
= 0°C to +105°C, unless otherwise noted. Typical values areat TA= +25°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.
IN to GND.................................................................-0.3V to +6V
C1+, SHDNto GND.......................................0.3V to (VIN+0.3V)
C1- to GND...............................................(VOUT- 0.3V) to +0.3V
OUT to GND.............................................................+0.3V to -6V
OUT Output Current............................................................90mA
OUT Short Circuit to GND..............................................Indefinite
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 7.4mW/°C above +70°C) (Note 1).....595mW
Junction-to-Case Thermal Resistance (θJC) (Note 1)
6-Pin SOT23 ................................................................39°C/W
Junction-to-Ambient Thermal Resistance (θJA) (Note 1)
6-Pin SOT23 ..............................................................134°C/W
Operating Temperature Range.........................-40°C to +105°C
Junction Temperature......................................................+150°C
Storage Temperature Range ............................-65°C to +150°C
Lead Temperature..........................................................(Note 2)
Note 1:Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Note 2:This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board-level solder attach and rework. Maxim recommends the use of the solder profiles recom-
mended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow
processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended.
PARAMETERCONDITIONSMINTYPMAXUNITSTA = +25°C1.45.5Supply Voltage RangeRL = 5kΩTA = 0°C to +105°C1.55.5V
Quiescent Supply CurrentTA = +25°C (Note 3)9501700µA
TA = +25°C0.0021Shutdown Supply CurrentVSHDN = 0TA = 0°C to +105°C0.03µA
Short-Circuit CurrentOutput shorted to ground, TA = +25°C170mA
Oscillator FrequencyTA = +25°C70125180kHz
Voltage Conversion EfficiencyIOUT = 0, TA = +25°C9999.9%
TA = +25°C1225Output ResistanceIOU T = 30m A ( N ote 4) TA = 0°C to +105°C36Ω
OUT-to-GND Shutdown ResistanceVSHDN = 0, OUT is internally pulled to GND
in shutdown38.5Ω
2.5V ≤ VIN ≤ 5.5V2.0SHDN Input Logic-HighVIN(MIN) ≤ VIN ≤ 2.5VVIN - 0.2V
2.5V ≤ VIN ≤ 5.5V0.6SHDN Input Logic-LowVIN(MIN) ≤ VIN ≤ 2.5V0.2V
TA = +25°C-100+0.05+100SHDN Bias CurrentSHDN = GND or INTA = 0°C to +105°C10nA
Wake-Up Time from ShutdownIOUT = 15mA100µs
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, C1 = C2 =2.2µF, VIN= VSHDN= +5V, VGND= 0, TA
= 0°C to +105°C, unless otherwise noted. Typical values areat TA= +25°C.)
Note 3:The MAX16945 may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee
proper startup, the input supply must be capable of delivering 90mA more than the maximum load current.
Note 4:Output resistance is guaranteed with capacitor ESR of 0.3Ω or less.
Note 5:All specifications from -40°C to +105°C are guaranteed by design, not production tested.
PARAMETERCONDITIONSMINTYPMAXUNITSSupply Voltage RangeRL = 5kΩ1.65.5V
Output CurrentContinuous, long-term60mARMS
Quiescent Supply Current(Note 3)1800µA
Oscillator Frequency60125200kHz
Output ResistanceIOUT = 30mA (Note 5)36Ω
OUT-to-GND Shutdown ResistanceVSHDN = 0, OUT is internally pulled to GND
in shutdown8.5Ω
2.5V ≤ VIN ≤ 5.5V2.1SHDN Input Logic-HighVIN(MIN) ≤ VIN ≤ 2.5VVIN - 0.2V
2.5V ≤ VIN ≤ 5.5V0.6SHDN Input Logic-LowVIN(MIN) ≤ VIN ≤ 2.5V0.2V
ypical Operating Characteristics(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN= VSHDN= +5V, VGND= 0, TA= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX16945 toc01
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +2V
VIN = +3.3V
VIN = +5V
EFFICIENCY vs. OUTPUT CURRENT
MAX16945 toc02
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +5V
VIN = +3.3V
VIN = +2V
OUTPUT IMPEDANCE
vs. INPUT VOLTAGE
MAX16945 toc03
INPUT VOLTAGE (V)
OUTPUT IMPEDANCE (
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
MAX16945SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX16945 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
PUMP FREQUENCY
vs. TEMPERATURE
MAX16945 toc07
TEMPERATURE (°C)
PUMP FREQUENCY (kHz)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX16945 toc05
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
VIN = +5V
VIN = +3.3V
VIN = +2V
OUTPUT IMPEDANCE
vs. TEMPERATURE
MAX16945 toc06
TEMPERATURE (°C)
OUTPUT IMPEDANCE (
VIN = +2V
VIN = +3.3V
VIN = +5V
2μs/div
OUTPUT NOISE AND RIPPLE10mV/div
MAX16945 toc08
40μs/div
STARTUP FROM SHUTDOWNVOUT
2V/div
MAX16945 toc09
SHDN
5V/div
Typical Operating Characteristics (continued)(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN= VSHDN= +5V, VGND= 0, TA= +25°C, unless otherwise noted.)
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
Detailed DescriptionThe MAX16945 capacitive charge pump inverts the
voltage applied to its input. For highest performance,
use low-ESR capacitors.
During the first half-cycle, switches S2 and S4 open,
switches S1 and S3 close, and capacitor C1 charges to
the voltage at IN (Figure 2). During the second half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is
level shifted downward by VINvolts. This connects C1
in parallel with the reservoir capacitor C2. If the voltage
across C2 is smaller than the voltage across C1,
charge flows from C1 to C2 until the voltage across C2
reaches -VIN. The absolute value of the inverting output
voltage is always smaller than the value of the input
voltage due to the losses of the flying capacitor C1 and
the resistance of the switches S1–S4.
OUTPUT RIPPLE
vs. CAPACITANCE
MAX16945 toc11
CAPACITANCE (μF)
OUTPUT RIPPLE (mV)
VIN = +4.375V, VOUT = -4V
VIN = +2.825V, VOUT = -2.5V
VIN = +1.7V, VOUT = -1.5V
Pin Description
Typical Operating Characteristics (continued)(Circuit of Figure 1, C1 = C2 = 2.2µF, VIN= VSHDN= +5V, VGND= 0, TA= +25°C, unless otherwise noted.)ON
OFF
C1+C1-
SHDN
OUT
GND
INPUT
1.5V TO 5.5VNEGATIVE
OUTPUT
-1 ✕ VIN
MAX16945
Figure 1. Typical Application Circuit3125678910
OUTPUT CURRENT
vs. CAPACITANCEMAX16945 toc10
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
VIN = +4.375V, VOUT = -4V
VIN = +2.825V, VOUT = -2.5V
VIN = +1.7V, VOUT = -1.5V
PINNAMEFUNCTION OUT Inverting Charge-Pump Output
2 IN Power-Supply Voltage Input. Input range
is 1.4V to 5.5V. C1- Negative Terminal of the Flying Capacitor
4 GND Ground SHDN
Shutdown Input. Drive SHDN high for
normal operation; drive SHDN low for
shutdown mode. OUT is actively pulled to
ground during shutdown. C1+ Positive Terminal of the Flying Capacitor S4
VOUT = -(VIN)
Figure 2. Ideal Voltage Inverter
MAX16945
30mA Inverting Charge Pump in SOT23
for EMI-Sensitive Automotive Applications
Efficiency ConsiderationsThe efficiency of the MAX16945 is dominated by its qui-
escent supply current (IQ) at low output current, and by
its output impedance (ROUT) at higher output current.
Efficiency is calculated as follows:
where the output impedance is roughly approximated by:
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
RSWis the sum of the charge pump’s internal switch
resistances (typically 4Ωto 5Ω at VIN= +5V). The typi-
cal output impedance is more accurately determined
from the Typical Operating Characteristics.
Current LimitThe MAX16945 limits its input current upon startup to
170mA (typ). This prevents low-current or higher output
impedance input supplies (such as alkaline cells) from
being overloaded when power is applied or when the
device awakes from shutdown.
ShutdownThe MAX16945 has a logic-controlled shutdown input.
Driving SHDNlow places the device in a low-power
shutdown mode. The charge-pump switching halts,
supply current is reduced to 2nA, and OUT is actively
pulled to ground through a 3Ωresistance.
Driving SHDNhigh will restart the charge pump. The
switching frequency and capacitor values determine
how soon the device will reach 90% of the input voltage.
Applications Information
Capacitor SelectionThe charge-pump output resistance is a function of the
ESR of C1 and C2. To maintain the lowest output resis-
tance, use capacitors with low ESR.
Flying Capacitor (C1)Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has negligible effect because the output
resistance is then dominated by internal switch resis-
tance and capacitor ESR.
Output Capacitor (C2)Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
Input Bypass Capacitor (C3)If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX16945’s
switching noise. An input bypass capacitor (C3) with a
value equal to that of C1 is recommended.
Voltage InverterThe most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion requires only two external components, capacitors
C1 and C2, plus an input bypass capacitor C3, if nec-
essary. See the Capacitor Selection section for sug-
gested capacitor sizes.I
2(f)C22IESRRIPPLEOUT
OSCOUTC2+××1 x C14ESRESROUT
OSCC1C2≅()++I1I x R
OUT
OUTQ
OUTOUT+−⎛⎜⎞⎟
fOSCRL
VOUT
Figure 3a. Switched-Capacitor Model
REQUIV =
REQUIV
VOUT
fOSC ✕ C1C2
Figure 3b. Equivalent Circuit
