MAX14578E_12 Datasheet, PDF (14/23 Pages) Maxim Integrated Products – USB Battery Charger Detectors

MAX14578E/MAX14578AE
USB Battery Charger Detectors
Detailed Description
The MAX14578E/MAX14578AE are USB charger detec-
tors compliant with USB Battery Charging Revision 1.1.
The USB charger-detection circuitry detects USB stan-
dard downstream ports (SDPs), USB charging down-
stream ports (CDPs), or dedicated charger ports (DCPs),
and controls an external lithium-ion (Li+) battery charger.
The MAX14578E features I²C communication, while the
MAX14578AE features an EN pin and an LDO output pin.
The internal USB switch is compliant to Hi-Speed USB,
full-speed USB, and low-speed USB signals. Both devic-
es feature low on-resistance, low on-resistance flatness,
and very low capacitance.
Input Sources and Routing
The typical Micro/Mini-USB connector has five signal
lines: USB power, two USB signal lines (D-, D+), ID line,
and ground. The USB power on the Micro/Mini-USB con-
nector connects to VB on the MAX14578E/MAX14578AE.
The two USB signal lines, D- and D+, connect to CD- and
CD+.
USB (CD-, CD+)
The MAX14578E/MAX14578AE support Hi-Speed
(480Mbps), full-speed (12Mbps), and low-speed USB
(1.5Mbps) signal levels. The USB channel is bidirectional
and has low 3.3I (typ) on-resistance and 4.5pF (typ)
on-capacitance. The low on-resistance is stable as the
analog input signals are swept from ground to VSWPOS
for low signal distortion.
LOUT LDO Output (MAX14578AE Only)
The LOUT LDO provides a 5.3V (typ) output, used to
power a USB transceiver. Most USB transceivers are
powered from a 3.3V or higher voltage that is difficult to
derive from a Li+ battery. One solution is to power the
transceivers from the USB VBUS power; however, VBUS
can rise as high as +28V in a fault condition. The LOUT
pin provides a voltage-limited supply that protects the
USB transceiver from these high voltages. When VBUS
rises above 9.0V (typ), the MAX14578AE detects an
overvoltage fault and LOUT goes to 0V. Additionally,
LOUT features a 100mA (typ) current limit to protect the
device in the event of a short circuit.
Interrupts
The MAX14578E generates an interrupt for any change in
VBCOMP, and when DBCHG or DCD_T transitions from
0 to 1. The INTEN bit in the CONTROL 1 register (0x01)
enables interrupt output. When INTEN is set to zero, all
interrupts are masked but not cleared. A read to the
INTERRUPT register (0x02) is required to clear interrupts.
Detection Debounce
To avoid multiple interrupts at the insertion of an acces-
sory and for added noise/disturbance protection, a
30ms (typ) debounce timer is present that requires an
inserted or removed state hold for the debounce time
before it sends an interrupt.
Low-Power Modes
The MAX14578E has two I²C bits in the CONTROL 1
register (0x01) dedicated to low-power operation:
LOW_POW and CP_ENA.
LOW_POW sets low-power mode. In low-power mode,
the internal oscillator is turned off under the following
conditions: no VBUS, USBSWC = 0, and CP_ENA = 0.
When enabled, all switches are high impedance (note
that no negative rail voltage can be applied).
CP_ENA controls the charge pump required for proper
operation of the analog switches. When set to disable,
no negative rail voltage can be applied. A factory default
sets CP_ENA = 0 automatically.
USB Charger Detection
The MAX14578E includes internal logic to detect if a valid
USB charger is connected. When a valid VBUS voltage is
applied to VB or when CHG_TYP_M in the CONTROL 1
register is set to 1, the MAX14578E/MAX14578AE begin
the charger-type-detection sequence (see Figure 1).
During the charger-type-detection sequence, the CD-
and CD+ switches are open, and once the sequence
completes, the switches return to their previous state.
Figure 2 shows a timing diagram for an example char-
ger-type-detection sequence.
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Maxim Integrated