User Manual

MAX6646/MAX6647/MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
10 ______________________________________________________________________________________
Conversion Rate Byte
The conversion rate register (Table 8) programs the time
interval between conversions in free-running autonomous
mode (RUN = 0). This variable rate control can be used
to reduce the supply current in portable-equipment appli-
cations. The conversion rate byte’s POR state is 07h or
4Hz. The MAX6646/MAX6647/MAX6649 look only at the 3
LSBs of this register, so the upper 5 bits are “don’t care”
bits, which should be set to zero. The conversion rate tol-
erance is ±25% at any rate setting.
Valid A/D conversion results for both channels are avail-
able one total conversion time (125ms nominal, 156ms
maximum) after initiating a conversion, whether conver-
sion is initiated through the RUN bit, one-shot com-
mand, or initial power-up. Changing the conversion rate
can also affect the delay until new results are available.
REGISTER ADDRESS POR STATE FUNCTION
RLTS 00h 0000 0000 0°C Read local (internal) temperature
RRTE 01h 0000 0000 0°C Read remote (external) temperature
RSL 02h N/A — Read status byte
RCL 03h 0000 0000 — Read configuration byte
RCRA 04h 0000 0111 — Read conversion rate byte
RLHN 05h 0101 0101 +85°C Read local (internal) ALERT high limit
RLLI 06h 0000 0000 0°C Read local (internal) ALERT low limit
0101 1111 +95°C Read remote (external) ALERT high limit (MAX6646/MAX6647)
RRHI 07h
0101 0101 +85°C Read remote (external) ALERT high limit (MAX6649)
RRLS 08h 0000 0000 0°C Read remote (external) ALERT low limit
WCA 09h N/A — Write configuration byte
WCRW 0Ah N/A — Write conversion rate byte
WLHO 0Bh N/A — Write local (internal) ALERT high limit
WLLM 0Ch N/A — Write local (internal) ALERT low limit
WRHA 0Dh N/A — Write remote (external) ALERT high limit
WRLN 0Eh N/A — Write remote (external) ALERT low limit
OSHT 0Fh N/A — One-shot
REET 10h 0000 0000 0°C Read remote (external) extended temperature
RIET 11h 0000 0000 0°C Read local (internal) extended temperature
0111 1101 +125°C Read/write remote (external) OVERT limit (MAX6646/MAX6647)
RWOE 19h
0101 0101 +85°C Read/write remote (external) OVERT limit (MAX6649)
RWOI 20h 0101 0101 +85°C Read/write local (internal) OVERT limit
HYS 21h 0000 1010 10°C Overtemperature hysteresis
QUEUE 22h 1000 0110 — Fault queue
— FEh 0100 1101 — Read manufacture ID
— FFh 0101 1001 — Read revision ID
Table 5. Command-Byte Bit Assignments
BIT NAME POR STATE FUNCTION
7 (MSB) MASK 0 Masks ALERT interrupts when set to 1.
6 RUN 0 Standby mode control bit; if set to 1, standby mode is initiated.
5 to 0 RFU 0 Reserved.
Table 6. Configuration-Byte Bit Assignments (03h)